This PR checks all active Action Cable documentation for typos and other
fixes. It aims to make sure that when Rails 5 is released, that the
Action Cable docs are up to snuff with the other documentation included
with Rails.

[ci skip]

[ci skip]

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

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.

[ci skip]

Since #23152 eliminated the EventMachine dependency, we don’t need to
explicitly mention EventMachine.

Nevertheless, I'm not 100% sure about saying "the websocket-driver loop"
driver… any suggestions, @matthewd or @pixeltrix ? 😅

[ci skip]

This changed in #22950.

I believe the paragraph starting with "This relies" belongs with the one above it.

* Clarify wording around how defaults work
* Clarify wording around what formatting versus information is required
* Separate consumer configuration section since it is important and wordy
* Add additional explanation of options for setting consumer configuration
* Consolidate consumer configuration information to reduce confusion

This reverts commit d0393fcc, reversing
changes made to 3b7ccadf.

Mounting it as prescribed here:

https://github.com/rails/rails/blob/0d1d50c2db40ea1a9d3bebfb0c35da43bbd4d27f/railties/lib/rails/generators/rails/app/templates/config/routes.rb#L5

* Add link to API documentation
* Link to issue tracker for rails/rails (instead of rails/actioncable)
* Add link to rails-core mailing list for feature requests

ActiveRecord -> Active Record [ci skip]

This will decouple Action Cable from Rails.

[ci skip]

Since Action Cable is getting integrated into rails/rails, the Travis
badge for rails/actioncable is not needed anymore.

Also following the standard of every other README to have `--` rather
than `-` to separating the name of the library from its description.

[ci skip] Getting to ready to merge into rails/rails

Thanks to feedback from @ascrazy, @jeremy, and @javan