Merge pull request #21 from Agrail/master

Changed all the DB quiery functions to work from the primarykey function within EMongoModel instead of assuming that _id is the only PK
Merge pull request #22 from Agrail/master

Add saveCounters() and an Advanced EMongoCriteria
Some formatting and comments in EMongoSort
Fix for issue: https://github.com/Sammaye/MongoYii/issues/24
Fix for: https://github.com/Sammaye/MongoYii/issues/24
Completed unit test for: https://github.com/Sammaye/MongoYii/issues/24
Merge branch 'master' of https://github.com/Sammaye/MongoYii

Conflicts:
	EMongoCriteria.php
	EMongoDocument.php