No need to expose classes to window context

Updated the sources that only in the prototype version the `Chosen` class is available in `window` context. The jQuery version only needs those classes internally.

This could only work when there is no separate function wrapper around every classes, which could easily be achieved by joining the coffee sources before compiling. (`join: true` in `Gruntfile.coffee`)

@harvesthq/chosen-developers; Was there a reason in the past that these classes were available in `window` context?