Normalized Ember.run.later and Ember.run.next behavior.

In particular, callbacks for both are now guaranteed to be run from
within a totally separate run loop; previously, though the docs
suggested so, there was no guarantee the code would be run from
within a run loop at all, much less a separate one.

Ember.run.next is now shorthand for Ember.run.later with
1ms wait, as a result, there was a chunk of `next` code
that could be removed/consolidated in to `later`.

Fixes #913
Merge pull request #2199 from machty/runloop-later

Normalized Ember.run.later and Ember.run.next behavior.
Update Gemfile.lock
Handle 'undefined' element properties - Fixes #2170
Update assert message for model hook in Ember.Route
Merge pull request #2216 from pangratz/update/assert_message

Update assert message for model hook in Ember.Route
Update ember-dev to fix tests
use charAt() instead of brackets to access string character
IE7 does not support bracket access to string characters and errors:
http://stackoverflow.com/questions/5943726/string-charatx-or-stringx
Merge pull request #2221 from craigteegarden/ie7-bracket-to-charAt

use charAt() instead of brackets to access string character
Added documentation to the append method

I know it's stated on the `rootElement` but I feel re-iterating it here is also helpful.

Fixed typo
Merge pull request #2222 from lsdafjklsd/patch-1

Added documentation to the append method
extract Ember.isEmpty into ember-metal

Ember computed.empty should always have identical semantics
Add Ember.computed.none… none + empty have different secants.

Also extract Ember.isNone into ember-metal
Ember.isArray implementation lives in ember-metal, its tests should also

Add test of Ember.isArray against an arrayProxy.
Merge pull request #2228 from stefanpenner/improve_many_small_things

Improve many small things
Stop using extended method

I used `Ember.String.fmt` instead of `String#fmt`.
Because the latter may be undefined.
Fix failing test

This package couldn't be required from test.
Merge pull request #2235 from tricknotes/fix-failing-test

Fix failing test
Better HistoryLocation popstate handling - Fixes #2234
Fix 'rake test[built]' task