Add date type for model attributes
Merge pull request #54 from bperel/master

Add date type for model attributes
Update PHPDoc
Merge pull request #55 from bperel/master

Update PHPDoc
Update save() and update() , supports for chain operation .
Update map() for chain operation.
Add save() and delete() methods.
Update README.md

Add save() and delete() for Collection.
Update map().
Fix issue with invalid ref in database
Merge pull request #60 from jrschumacher/fix-invalid-ref

Fix issue with invalid ref in database