* Done primarily so postprocessors would work properly
(i.e. sprockets-commonjs)
* Potentially eliminates need for all the JHW specific template
engines, except NilTemplate
* Allows for manipulation of the Sprockets::Environment for
things like adding/removing pre/postprocessors from spec_helper.rb
* Also, fixed specs that were failing on files_list.rb when
run standalone due to missing require in file_checker.rb
