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.
Done.