Don't call toString at extend time

Doing so will memoize the function so that any Ember.View subclass will return the same value for toString.
Add Ember.setupForTesting.

This makes it somewhat easier to unit-test Ember. It also gives us a
good place to add additional customization (as opposed to advocating
simply setting `Ember.testing = true`).
Enable features given a 'go' status.

New features as of 2014/01/17:

* `ember-testing-routing-helpers`
* `ember-testing-triggerEvent-helper`
* `computed-read-only`
* `ember-metal-is-blank`
* `ember-eager-url-update`

Also, removed `composable-computed-properties` as it was accidentally
commited in another unrelated PR.
Fixes a typo in the `Ember.Mixin` documentation.
Drop file with un-used observer and childContainer cleanup
[FEATURE query-params-new] Only scope conflicting query params
Fix slight documentation typo
Merge pull request #4186 from raytiley/qp-changes

[FEATURE query-params-new] Only scope conflicting query params
Merge pull request #4188 from josepjaume/patch-2

Fix slight documentation typo
Fix a couple of document typos in enumerable
Merge pull request #4184 from mixonic/drop-childContainers

Drop un-used observer and childContainer cleanup
Merge pull request #4191 from fanta/enumarable_typos

[DOC beta] Fix a couple of documentation typos in enumerable
[DOC beta] Document the send method on Ember.ActionHandler
[FEATURE query-params-new] alias computed.reads as computed.oneWay

oneWay is ambiguous. Which way?

Ember.computed.alias is a way more semantically meaningful alias of
Ember.computed.oneWay.

Example: http://jsbin.com/ucanam/3000

Putting this in query params because I'd like to use this
in some of the examples for query params; seems like it'll be
common lightweight pattern for buffering small changes, and
oneWay is just enough of a mental hurdle to necessitate this.
Merge pull request #4112 from machty/computed-reads

[FEATURE query-params-new] alias computed.reads as computed.oneWay
Merge pull request #4192 from bmac/action-handler-send-docs

[DOC beta] Document the send method on Ember.ActionHandler
Update CHANGELOG.md for 1.4.0-beta.3.
[BUGFIX BETA] BREAKING: Fixed how parentController property of an itemController when nested.

When an `itemController` is specified for an ArrayController that itself has a `parentController`
set, the framework was previously setting the itemController's `parentController` property to the
ArrayController's `parentController` instead of the ArrayController itself. This commit fixes that
behavior, and improves the docs, naming, and logic around this case.

If you were relying on an itemController's `parentController` skipping a generation, you will
need to use `parentController.parentController` or better yet, avoid the Law of Demeter
violation and provide a sensible method on the ArrayController that itself delegates to its
`parentController`.
Merge pull request #4183 from KasperTidemann/master

Fixes a typo in the `Ember.Mixin` documentation.
Merge pull request #4159 from rjackson/add_ember_setupForTesting

Add Ember.setupForTesting.