This will fix the problem on the CI server, where some time the change occurred by "write_file" will not trigger Rubinius to generate a compiled .rbc file.

Closes #602

This test will generate a basic Rails application, include Paperclip
into Gemfile, and call basic `has_attached_file` in the model. This will
make sure that we're not messing up any of the configuration and
integration for our gem and the Rails framework.