[FEATURE em-o] Added `Em.O` (shorthand for `Ember.Object.create`
[BUGFIX beta] Fixes issue when content is undefined for Ember.Select with optgroup

If the content given is undefined at the time of initialization, and
later changed,
`Ember.Select` correctly renders an empty select and then updates the
content  [Example](http://jsbin.com/epodAwU/14/edit),
But `Ember.Select` with `optgroup` breaks.
[Example](http://jsbin.com/IJaToVO/1/edit).

This breakage may happen, when the content for the select is fetched
via an ajax call to the server.

This PR fixes it.
Update route recognizer
Fix documentation for Ember.Select multiple and disabled attributes
[BUGFIX beta] Calling `replaceIn` would incorrectly move views from the `hasElement` to `inDOM`
[BUGFIX beta] Optimization: Clear the meta cache without using observers.
Add an extra space to fix the list formatting in the input helper docs
Merge pull request #3413 from bmac/fix-input-helper-checkbox-formatting

Add an extra space to fix the list formatting in the input helper docs
Merge pull request #3104 from eviltrout/view_observers

[BUGFIX beta] Optimization: Clear the meta cache without using observers.
Add instantiate example to App.register
Merge pull request #3417 from BlakeWilliams/instantiate-example

Add instantiate example to App.register documentation
fix a typo in container docs
Merge pull request #3420 from goshakkk/container-docs-typo

Fix a typo in container docs
Adding comments for 'extend()' method

Additional comments

Added comments for Mixins

Added example using Ember.Mixin

Added some description of create() vs extend()
Fixed documentation of computed.mapBy. Typos and removed unreferenced second computed property
Merge pull request #3389 from graup/docu-computed

Fixed documentation of computed.mapBy.
add a 'readonly' binding to TextSupport
Merge pull request #3423 from goshakkk/text-support-readonly

Add a 'readonly' binding to TextSupport
Test with all feature flags enabled.
Fix documentation and inconsistent usage for Ember.deprecateFunc()