First steps for mongo_mapper support
Modified hooks test to avoid problems with MongoMapper's proxy
Added mongo_mapper environment config for Travis
Moved MongoMapper test config to a YAML file
Updated comments on MongoMapper's module
implement rendering activities in collections

saves developers from having to loop over everything to render it.
relies on Enumerable support on ORM's querying interface.
is backward compatible and works for single activities or collections.
Update README.md
Merge pull request #101 from julioolvr/mongomapper-support

MongoMapper support
Merge branch 'master' into rails4

Conflicts:
	Gemfile