Migrate mongoid

Migrated from MongoMapper to Mongoid.  I also specified database names which are a bit more descriptive.
Note: the rocket operator (=>) is the old way of doing symbol hash mappings.  In Ruby 1.9+, it is preferred to use the syntax I gave below.  So, instead of {:default => 1}, use {default: 1} instead.  Ref: http://breakthebit.org/post/8453341914/ruby-1-9-and-the-new-hash-syntax