[BUGFIX release] `Ember.SubArray` operation composition fix.

In the case where `SubArray` would compose-left, the index was left unchanged,
and we would attempt to compose-right with bad assumptions about what operation
we were composing.
fix initializer assertion messages

(@stefanpenner / @rjackson)
[BUGFIX] Fix an issue with concatenatedProperties.

This commit fixes an issue with how contactedProperties are applied that
can result in subclasses sharing a reference to the same array, in a
surprising way. As an example, the failing test provided here shows
how two Ember.App subclasses shares were sharing inadvertently
sharing initializers.

Thanks to @kselden and @stefanpenner for code review.
[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.
[BUGFIX beta] Fixes #3332 - Array Computed Properties should update synchronously
Update to the latest ember-dev.

Major new features:

* Automated multi-branch testing for commits with specially formatted
  commit messages (BUGFIX, SECURITY, etc).
* Documentation generator via `rake docs` task.
* Automatic publishing of generated docs for each build.
* Will wait for the Rack server to be ready for connections before
  initiating tests (hopefully mitigates the phantomjs timeout issue)
* Will test each package both with and without feature flags.
* Will abort tests if `defeatureify` is not present and a
  `features.json` file exists.
* Updates to QUnit 1.12.0.
* Updates to use Puma for automated tests.
* Many test improvements.
Revert "[BUGFIX] Fix an issue with concatenatedProperties."

This caused some regressions and will be fixed correctly soon.

This reverts commit 8f5356d1513e334a6d29c9d97541eda97a39d635.
Update CHANGELOG
Merge pull request #3496 from rjackson/update_beta_changelog

Update beta changelog.