Bugfix/chosen 1.x compatibiliy

This PR makes the necessary changes to Ajax Chosen to make it compatible with Chosen 1.0.0 (but not compatible anymore with 0.x versions).

A quote from the Chosen 1.0.0 release notes:

> * All CSS class names have been renamed from a `chzn-` root to a `chosen-` root.
> * All custom Chosen events starting with `liszt` are now prefaced with a `chosen:`

All files have been updated: the CoffeeScript one, the JS one, and the minified JS version.