[DOC Beta] New behaviour with itemController

This [BUGFIX beta - Ensure context is unchanged when using keywords with itemController.](https://github.com/emberjs/ember.js/pull/4636) changed the way `itemController` behaves inside `#each` helper. I had problems making it work out because documentation doesn't clear this out and I had to debug it.

These two JsBins describe what changed from the developer using `#each` helper with `itemController`.

- [JsBin with Ember (1.5.1)](http://jsbin.com/ucanam/4838/edit) -> we can call itemController's property without prepending `person`

- [JsBin with Ember (1.6.0-beta.3)](http://jsbin.com/ucanam/4837/edit) -> if we don't prepend `person` for itemController's property we won't get result
Merge pull request #4802 from zigomir/patch-2

[DOC Beta] New behaviour with itemController
[BUGFIX beta] Don't fire redirect on parent routes

We've decided this is just going to be merged
into beta, not release.

Closes #4692
Fix small code styling inconsistencies with CONTRIBUTING.md
Fix issue with Travis using 2.1.0.
Merge pull request #4809 from dentuzhik/fix-styling

Fix small code styling inconsistencies with CONTRIBUTING.md
More Travis shenanigans.
Merge pull request #4796 from machty/parent-redirect

[BUGFIX release] Don't fire redirect on parent routes
[BUGFIX beta] Convert thrown strings into Ember.Errors
Merge pull request #4812 from duereg/master

Convert thrown strings into Ember.Errors