Ruby 1.8.7 backwards-compatibility

# Don't Merge this into master

You may not want to use it at all. I just need it, and thought you might be interested.

To make rolify ruby 1.8.7 compatible, I pulled all traces of Mongoid out of the code (minus the changelog).

Beyond that, there were two hash syntax conversions.

All specs pass. If you're interested in using this branch, please double-check my removals in the specs. I'm not familiar with Rspec, and only looked at the specs in passing, so I may have cut something important.

Thanks for creating this in the first place!