[BUGFIX beta] Force remove `required` attribute for IE8

In IE8, `elem.prop('required', '')` couldn't remove attribute.
(This problem is occured at `required` only. Other attributes work as our
expectation.)

``` javascript
view.set('required', false);
view.$().get(0).outerHTML; // this includes `required` attribute.
```

To remove attribute, `removeProp` is needed.
Made Ember.compare() test more readable
Split ember-routing handlebars integration off into ember-routing-handlebars
Merge pull request #5004 from mmun/ember-routing-handlebars

ember-routing-handlebars
update ember-cli version
Merge pull request #5008 from stefanpenner/update-ember-cli

update ember-cli version
[DOC release] Minor grammar error

Minor grammar error in RenderBuffer docs.
Merge pull request #5009 from chadhietala/patch-1

[DOC release] Minor grammar error
Removed trailing commas to ensure vintage IE compatibility
Merge pull request #5012 from crismali/removed-trailing-commas

Removed trailing commas to ensure vintage IE compatibility
[DOC release] Documents Application.initializer
Merge pull request #4935 from locks/application-initializer-documentation

[DOC release] Fixes #4934 - "Ember.Application.prototype.initializer is not documented."
[FEATURE query-params-new] Model dep state and bugfixes

Query params values are stored in an application cache
using cache keys calculated from Route#serialize params.
At some point this concept will be generalized, but
for now, only query params have model dependent state.
Merge pull request #4898 from machty/qp-may

[FEATURE query-params-new] Model dep state and bugfixes
Merge pull request #5002 from crismali/make-ember-compare-test-more-readable

Made `Ember.compare()` test more readable
Throw error if improperly defined factory
Merge pull request #5022 from knownasilya/container-inst-error

Throw error if improperly defined factory
another pass to improve es6 module usage
Merge pull request #5010 from stefanpenner/es6-cleanup

Es6 cleanup
Ensure that `DefaultResolver` is exported properly.