Create initial MongoDB implementation
This impkementation only implements the MongoDB driver and is still restricted to the original two dimentional design.  Because of this only references at the root level of the document can be resolved in a relationship.
Update README.md

Remove pearhub form readme since that is some broke ass crap
Add tests for different object types
Add multi-level default/override merge
Added multi-level merging of override data into default data to
better handle document based data stores.
Add doc comments to Store interface
Added tests and improved error handling for Mongo driver
Added additional integration tests to ensure objects are handled properly.
Added additional integration tests to ensure relationships are properly handled
with the Mongo driver.
Added machinist\Error translation for all Mongo exceptions
Update namespace and composer info for DerpTest
Update namespace and composer info for DerpTest
Merge branch 'doctrine-mongodb'