🎉 🍻

```
# before
App.appearance = App.cable.subscriptions.create "AppearanceChannel",
  connected: ->
    # Called when the subscription is ready for use on the server

  disconnected: ->
    # Called when the subscription has been terminated by the server

  received: (data) ->
    # Called when there's incoming data on the websocket for this channel

  appear: ->
    @perform 'appear'
  away: ->
    @perform 'away'
```

```
# after
App.appearance = App.cable.subscriptions.create "AppearanceChannel",
  connected: ->
    # Called when the subscription is ready for use on the server

  disconnected: ->
    # Called when the subscription has been terminated by the server

  received: (data) ->
    # Called when there's incoming data on the websocket for this channel

  appear: ->
    @perform 'appear'

  away: ->
    @perform 'away'
```

Logging Action Cable to STDOUT caused the development log to see double
messages like this:

```
Started GET "/" for ::1 at 2015-12-17 15:21:34 -0500
Started GET "/" for ::1 at 2015-12-17 15:21:34 -0500
Processing by Rails::WelcomeController#index as HTML
Processing by Rails::WelcomeController#index as HTML
Rendered /welcome/index.html.erb (0.0ms)
Rendered /welcome/index.html.erb (0.0ms)
Completed 200 OK in 3ms (Views: 1.3ms | ActiveRecord: 0.0ms)
Completed 200 OK in 3ms (Views: 1.3ms | ActiveRecord: 0.0ms)
```

Now that Action Cable is part of Rails it doesn't need it's own logger
and will log to STDOUT via the local dev server here:
https://github.com/rails/rails/blob/master/railties/lib/rails/commands/server.rb

Warnings coming from code and test are removed

Fix typo

Assume that the cable server is running in-process by default, offer option to change that in config/environments/production.rb

Indeed we need this to be an engine for the internal assets to work

It should be configured through the railtie

This will decouple Action Cable from Rails.

Otherwise assets will not work

The application can have more than one ApplicationController and we
want Action Cable helpers in all controllers and their views so we
should hook in the same place that others helpers.