Ember.Select shouldn't trigger change for when content is an empty array-like obejct
The previous check for triggering when content was empty relied on
the falsiness of `[]` but would incorrectly trigger change when the
content was an Array-like object whose proxied `length` was 0.

Specifically this would cause issues with setting the `contentBinding`
of a Select to the `DS.Model.find` values that are empty initially
setting the Select's `selection` from whatever the current value is to
`undefined` when change was triggered on an empty content.

Asynchronously, data would return and the content would become populated
but the selection value had already been unset.
Make outlets work inside block helpers
Always bind outlet to the template from whence it came
Adding unit test for nested outlets
Added VagrantFile and chef cookbooks to ease ember build for developers.
Doc explaining how to build ember with Vagrant VM
Update gitsubmodules urls to public repos.
Merge pull request #1708 from bobey/master

Added a VagrantFile to ease emberjs build for newcomers
Update gitignore.
Remove pointless check for native Array replace.

The real function is called splice, which is what the “shim” was calling anyway.
Move PromiseChain to old-router
Merge pull request #1715 from CrowdStrike/promise-chain-cleanup

Move PromiseChain to old-router
ArrayController learned itemControllerClass.

```javascript
App.ItemController =
  Em.ObjectController.extend();

var arrayController = Em.ArrayController.create({
  itemControllerClass: 'ItemController',
  content: Em.A([0, 1])
});

controller.objectAtContent(0);               // an instance of ItemController
controller.objectAtContent(0).get('content') // 0
```

This partially addresses #1637, but makes no attempt at supporting reusable
views.
Allow chaining on DeferredMixin#then
Merge pull request #1718 from CrowdStrike/deferred-chaining

Allow chaining on DeferredMixin#then
Merge branch 'arrayproxy-itemcontrollersclass' of https://github.com/hjdivad/ember.js into hjdivad-arrayproxy-itemcontrollersclass
Cleanup before merge
Clarify itemController out of range case.
Merge branch 'nested-outlets' of https://github.com/ef4/sproutcore20 into ef4-nested-outlets

Conflicts:
	packages/ember-handlebars/lib/ext.js
Merge branch 'master' of github.com:emberjs/ember.js