remove description of `render :nothing` from guide [ci skip]

`:nothing` option was deprecated in 44781b6e

Fix typo [ci skip]

For better or worse, anonymous `*` args will allocate arrays.  Ideally,
the interpreter would optimize away this allocation.  However, given the
number of times we call `html_safe` it seems worth the shedding idealism
and going for performance.  This line was the top allocation spot for a
scaffold (and presumably worse on real applications).

```
[aaron@TC rails (master)]$ cat xor.rb
a = "\x14b\"\xB4P8\x05\x8D\xC74\xC3\xEC}\xFDf\x8E!h\xCF^\xBF\xA5%\xC6\xF0\xA9\xF9x\x04\xFA\xF1\x82"
b = "O.\xF7\x01\xA9D\xA3\xE1D\x7FU\x85\xFC\x8Ak\e\x04\x8A\x97\x91\xD01\x02\xA4G\x1EIf:Y\x0F@"

def xor_byte_strings(s1, s2)
  s1.bytes.zip(s2.bytes).map { |(c1,c2)| c1 ^ c2 }.pack('c*')
end

def xor_byte_strings2(s1, s2)
  s2_bytes = s2.bytes
  s1.bytes.map.with_index { |c1, i| c1 ^ s2_bytes[i] }.pack('c*')
end

require 'benchmark/ips'
require 'allocation_tracer'

Benchmark.ips do |x|
  x.report 'xor_byte_strings' do
    xor_byte_strings a, b
  end

  x.report 'xor_byte_strings2' do
    xor_byte_strings2 a, b
  end
end

ObjectSpace::AllocationTracer.setup(%i{type})
result = ObjectSpace::AllocationTracer.trace do
  xor_byte_strings a, b
end
p :xor_byte_strings => result
ObjectSpace::AllocationTracer.clear
result = ObjectSpace::AllocationTracer.trace do
  xor_byte_strings2 a, b
end
p :xor_byte_strings2 => result
[aaron@TC rails (master)]$ ruby -I~/git/allocation_tracer/lib xor.rb
Calculating -------------------------------------
    xor_byte_strings    10.087k i/100ms
   xor_byte_strings2    11.339k i/100ms
-------------------------------------------------
    xor_byte_strings    108.386k (± 5.8%) i/s -    544.698k
   xor_byte_strings2    122.239k (± 3.0%) i/s -    612.306k
{:xor_byte_strings=>{[:T_ARRAY]=>[38, 0, 0, 0, 0, 0], [:T_STRING]=>[2, 0, 0, 0, 0, 0]}}
{:xor_byte_strings2=>{[:T_ARRAY]=>[3, 0, 0, 0, 0, 0], [:T_DATA]=>[1, 0, 0, 0, 0, 0], [:T_IMEMO]=>[2, 0, 0, 0, 0, 0], [:T_STRING]=>[2, 0, 0, 0, 0, 0]}}
```

[ci skip] Fix grammar

fix 'method redefined' warnings

Fix a typo

Replace `a` with `an`

This reverts commit 8c3cca5e, reversing
changes made to 9dcf67c4.

Reason: https://github.com/rails/rails/pull/23562#issuecomment-181442569

Update rails-html-sanitizer version to  v1.0.3

rails-html-sanitizer 1.0.2 is vulnerable: https://groups.google.com/d/msg/rubyonrails-security/uh--W4TDwmI/m_CVZtdbFQAJ

Remove references to Rails 4 from assets guide [ci skip]

revert dev:cache to rake task, fixes #23410

Add numeric type in the doc [ci skip]

Follow up to #23508.

remove `faye-websocket` dependency from README [ci skip]

`faye-websocket` gem is no longer used from 322dca29.

config examples for ActionCable now use Rails.application.config.action_cable

update turbolinks url [ci skip]

`schema_type` returns symbol rather than string

Some existing examples used ActionCable.server.config but for
configuring allowed_request_origins that is overridden in development
mode. The correct place to set that is
Rails.application.config.action_cable which the ActionCable initializer
loads from. I thought the other two examples should be changed as well
just in case a default value that would override a configured value is
introduced for either log_tags or disable_request_forgery_protection in
the future.

Added numeric helper into `SchemaStatements` for MySQL and PostgreSQL

doc changes to clarify asset pipeline

for rails/rails#23431

       modified:   guides/source/asset_pipeline.md
* description of asset combination from apps and gems, e.g. jquery-rails
* after @vipulnsward's related change rails/rails#23479
  correction: --skip-sprockets will prevent all of these gems, not just sass-rails and uglifier

       modified:   guides/source/working_with_javascript_in_rails.md
* noted that rails.js requires the asset pipeline

[ci skip]

Hand off the interlock to the new thread in AC::Live

A return value of `schema_type` is used by:

1. primary key type: using as `symbol.inspect`
2. normal column type: using as `symbol.to_s`

It is better to return symbol.

A full write-preferring wait can lead to deadlock.

Publish guide on "Using Rails for API-only Applications"

Fixes #23322
[ci skip]

[ci skip]