To be 'mongoid-slug', notice the hyphen. Issue #179

Naming fix for the new gem, with hyphen (to be registered with rubygems).
My suggestion is that the current be moved to a underscore branch, keeps the github name correct.
And a new release of the old gem with deprecated notice. #179
As a side note: It's ugly as hell, but the naming of paranoia should be mongoid-paranoia2
Really confuse for the new user this. (I only understood when I read https://github.com/haihappen/mongoid-paranoia README) .  Hehe name it paranoid ... it's more rock'n roll ;)