Implement dynamic locale lookup.

Allow dynamic locale lookup and rerendering when the `application.locale` value changes.

* Requires 1.9.0-beta.3.
* Removes `t` utility function (it was not usable standalone).

Closes #1.

@bcardarella - This is a fairly significant refactor. Please feel free to close this PR and reimplement using this as inspiration on how to get the rerendering to work.
Yes, they are. When Ember was streamified these methods/classes were not exposed in the globals build (which was a mistake IMHO). I have submitted https://github.com/emberjs/ember.js/pull/9693 to expose them (hopefully in 1.10 since they will be needed for dealing with HTMLBars helpers).

To avoid using the private loader/register I can reimplement here instead, but that seemed somewhat odd also.