This handler simply allows arbitrary Ruby code as a template

The separation option enable to keep entire words, lines or anything.
To split by line, like github, we can set the separation option as \n.
To split by word, like google, we can set the separation option as " ".
The radius option represent the number of lines or words we want to
have in the result.
The default behaviour is the same. If we don't set the separation
option, it split the text any where.

There is no memcache gem left in repo.

`parse` method performance improvements - ~27-33%:

    accept = "image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword,  , pronto/1.00.00, sslvpn/1.00.00.00, */*"

    Benchmark.measure{ 1_000_0.times { Mime::Type.parse(accept) }}

    old: 1.430000   0.000000   1.430000 (  1.440977)
    new: 0.920000   0.000000   0.920000 (  0.921813)

Also, add documentation for alternate usage.

This allows us to make alterations to the generated routes based on the
scope of the current mapper, and otherwise allows us to move larger
blocks of concerns out of the routes file, altogether.

This reverts commit 7256cb53, reversing
changes made to 6ebe22c3.

Reason: A test was failing.

This reverts commit e4b33b08.

https://github.com/rails/rails/pull/7452#issuecomment-8094302

Added controller-level etag additions that will be part of the action etag computation *Jeremy Kemper/DHH*

Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) *DHH*

Many named routes have keys that are required to successfully resolve. If a key is left off like this:

    <%= link_to 'user', user_path %>

This will produce an error like this:

    No route matches {:action=>"show", :controller=>"users"}

Since we know that the :id is missing, we can add extra debugging information to the error message.

    No route matches {:action=>"show", :controller=>"users"} missing required keys: [:id]


This will help new and seasoned developers look closer at their parameters. I've also subclassed the routing error to be clear that this error is a result of attempting to generate a url and not because the user is trying to visit a bad url. 

While this may sound trivial this error message is misleading and confuses most developers. The important part isn't what's in the options its's what's missing. Adding this information to the error message will make debugging much more obvious. 

This is the sister pull request of https://github.com/rails/journey/pull/44 which will be required to get they missing keys into the correct error message. 

Example Development Error in Rails: http://cl.ly/image/3S0T0n1T3421

Methods provided by RecordIdentifier are not widely used in controllers
nowadays as they're view specific (this is probably a legacy left after
RJS rendering directly in controllers). However if people still need to
use it, it's trivial to include ActionView::RecordIdentifier by
themselves.

We extend it with self, but the methods were not working properly were
used directly on module.

ActionDispatch::Routing::UrlFor was always required in UrlHelpers. This
was changed by splitting previous implementation of UrlHelper into 2
modules: ActionView::Helpers::UrlHelper and
ActionView::Routing::UrlHelper. The former one keeps only basic
implementation of url_for. The latter adds features that allow to use
routes and is only required when url_helpers or mounted_helpers are
required.

default_formats array is used by LookupContext in order to allow
rendering templates when :formats option is not passed. Previously it
was always set to Mime::SET, which created dependency on Action Pack. In
order to remove this dependency, Mime::SET is used only if
ActionController is loaded.

Automatically handling mime types for things other than :rss and :atom
is not functionality that justifies dependency on Mime::Type from
actionpack.

We can use another way to instantiate ActionView::Base, by passing
renderer as a first option. Thanks to that we can just pass prefixes to
LookupContext instead stubbing them on the controller. This is also good,
because that kind of API is used in Rails code.

This is another step in moving Action View's dependencies in Action Pack
to Action View itself. Also, HtmlScanner seems to be better suited for
views rather than controllers.

Since it's more about DOM classes and ids it belongs to Action View
better. What's more, it's more convenient to make it part of Action View
to follow the rule that Action Pack can depend on Action View, but not
the other way round.

There is no memcache gem left in repo.

Instead of building a Blog::Post instance for every test in form helper
tests, just build it in the test that uses it.

we should take disabled option not only from `html_options` hash but from
`options` hash too like `build_select` method does it. So

datetime_select("post", "updated_at", { :discard_minute => true }, { :disabled => true })
datetime_select("post", "updated_at", :discard_minute => true , :disabled => true)

both these variants work now

closes #7431

This functionality will be available from gem
`active_record-session_store` instead.