Fix doc of limit option for a text column [ci skip]

Follow up #21591.

The document of limit option for a text column is incorrect.

MySQL: the limit is byte length, not character length
Pg, Sqlite3: variable unlimited length

Fix HSTS default expire in ActionDispatch::SSL docs.

fix typo intance -> instance in ActionView [ci skip]

`intance` should be `instance`

TEXT and BLOB limit is byte length, not character length.

Updated MySQL documentation link to MySQL latest version 5.7 everywhe…

Improving `in_time_zone` docs [ci skip]

`DateTime.utc` is not a valid method. It gives `NoMethodError: undefined method `utc` for DateTime:Class`. As we know that we can calculate `utc` time from `Time` Class, but we can’t calculate `utc` time from `DateTime` Class.

Ruby 2.2.3 in windows need nokogiri 1.6.7.rc3

dev and edge have some common, so factor it out.

Ruby 2.2.3 in windows need nokogiri 1.6.7.rc3 as it's the only version having correct pre-compiled so

Improve String#strip_heredoc

Saves about 6 MB, about 40% faster.

**strip_heredoc.rb**

```ruby
require "active_support/core_ext/object/try"
require "get_process_mem"

class String
  def strip_heredoc
    indent = scan(/^[ \t]*(?=\S)/).min.try(:size) || 0
    gsub(/^[ \t]{#{indent}}/, '')
  end
end

if ENV["MEASURE_MEMORY"] == "yes"
  mem = GetProcessMem.new
  GC.start
  GC.disable
  10000.times do
    <<-MSG.strip_heredoc
      xhr and xml_http_request methods are deprecated in favor of
      `get :index, xhr: true` and `post :create, xhr: true`
    MSG
  end
  before = mem.mb

  after = mem.mb
  GC.enable
  puts "Before: #{before} MiB"
  puts "After: #{after} MiB"
  puts "Diff: #{after - before} MiB"
end
```

**patched_strip_heredoc.rb**

```ruby
require "active_support/core_ext/object/try"
require "get_process_mem"

class String
  def patched_strip_heredoc
    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze)
  end
end

if ENV["MEASURE_MEMORY"] == "yes"
  mem = GetProcessMem.new
  GC.start
  GC.disable
  10000.times do
    <<-MSG.patched_strip_heredoc
      xhr and xml_http_request methods are deprecated in favor of
      `get :index, xhr: true` and `post :create, xhr: true`
    MSG
  end
  before = mem.mb

  after = mem.mb
  GC.enable
  puts "Before: #{before} MiB"
  puts "After: #{after} MiB"
  puts "Diff: #{after - before} MiB"
end
```

**Before**

```
$ MEASURE_MEMORY=yes ruby strip_heredoc.rb
Before: 44.73828125 MiB
After: 44.7734375 MiB
Diff: 0.03515625 MiB
```

**After**

```
$ MEASURE_MEMORY=yes ruby patched_strip_heredoc.rb
Before: 37.9765625 MiB
After: 38.015625 MiB
Diff: 0.0390625 MiB
```

`44.7734375 -  38.015625 = 6.75`

=> **Saves about 6.75 MiB**

**benchmark.rb**

```ruby
require "benchmark/ips"
require_relative "./strip_heredoc"
require_relative "./patched_strip_heredoc"

def original
  <<-MSG.strip_heredoc
    xhr and xml_http_request methods are deprecated in favor of
    `get :index, xhr: true` and `post :create, xhr: true`
  MSG
end

def patched
  <<-MSG.patched_strip_heredoc
    xhr and xml_http_request methods are deprecated in favor of
    `get :index, xhr: true` and `post :create, xhr: true`
  MSG
end

Benchmark.ips do |x|
  x.report("original") { original }
  x.report(" patched") { patched  }
  x.compare!
end
```

```
$ ruby -v benchmark.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]
Calculating -------------------------------------
            original     5.652k i/100ms
             patched     6.477k i/100ms
-------------------------------------------------
            original     54.076k (± 5.7%) i/s -    271.296k
             patched     74.557k (± 6.2%) i/s -    375.666k

Comparison:
             patched:    74557.0 i/s
            original:    54076.4 i/s - 1.38x slower
```

=> **About 38% faster**

1. Clone rails project `git clone git@github.com:rails/rails.git`
2. Apply this patch to
`activesupport/lib/active_support/core_ext/string/strip.rb`
3. `cd activesupport`
4. run `rake`
5. And tests passed:

```
➜ activesupport $ rake
/Users/Juan/.rubies/ruby-2.2.2/bin/ruby -w -I"lib:test"
"/Users/Juan/.rubies/ruby-2.2.2/lib/ruby/2.2.0/rake/rake_test_loader.rb"
 "test/**/*_test.rb"

........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
........................................................................
......................................................................S.
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Finished in 15.343004s, 214.2344 runs/s, 24902.4898 assertions/s.

3287 runs, 382079 assertions, 0 failures, 0 errors, 48 skips

You have skipped tests. Run with --verbose for details.
```

Remove RHTML reference in Action Controller docs

Remove wrong doc line about AC::Parameters

AC::Parameters does not inherit from HashWithIndifferentAccess
since #20868 by @sikachu

add description of passing a block to `add_source` [ci skip]

block support added in 8cc01e0b

autoloading this could possibly cause some weird race condition
when calling an AR::Attribute's singleton method on a threaded server.

Bumps from `5.6` to `5.7`

fix wrong method used in the TimeWithZone#inspect method docs [ci skip]	

Improve the AR querying docs

Bumps to 5.7

* rewords a few awkwardly worded sentences
* adds some punctuation
* adds a few missing words

The last call site of `last_version` was removed with:

838e1832

`Rack::Session::Abstract::ID` is now deprecated and
`Rack::Session::Abstract::Persisted` should be used instead.

In c546a2b0 this was changed to mimic how the browser behaves in a real
situation but left out types that were registered.

When this was changed it didn't take `text/plain` or `text/html` content
types into account. This is a problem if you're manipulating the
`Content-Type` headers in your controller tests, and expect a certain
result.

The reason I changed this to use `to_sym` is because if the
`Content-Type` is not registered then the symbol will not exist. If it's
one of the special types we handle that specifically (:json, :xml, or
:url_encoded_form). If it's any registered type we handle it by setting
the `path_parameters` and then the `request_parameters`. If the `to_sym`
returns nil an error will be thrown.

If the controller test sets a `Content-Type` on the request that `Content-Type`
should remain in the header and pass along the filename.

For example:
If a test sets a content type on a post
```
@request.headers['CONTENT_TYPE'] = 'text/plain'
post :create, params: { name: 'foo.txt' }
```

Then `foo.txt` should be in the `request_parameters` and params related
to the path should be in the `path_parameters` and the `Content-Type`
header should match the one set in the `@request`. When c546a2b0 was
committed `text/plain` and `text/html` types were throwing a "Unknown
Content-Type" error which is misleading and incorrect.

Note: this does not affect how this is handled in the browser, just how
the controller tests handle setting `Content-Type`.

HasManyAssociation: moved half of counter cache code to reflection

Use `ActiveRecord::Tasks::DatabaseTasks.migrations_paths` explicit for db tasks

This method is private API and never used. Let's remove it.

`Schema#migrations_paths` is not supposed to be public API. In fact
it's only used inside `Schema` itself, so let's make it private.

It is always passed in