Updates sql-query dependency to 0.0.11
Adds Model.aggregate()
Adds necessary support for Model.aggregate() to all drivers
Adds test for Model.aggregate()
Updates Readme to show an example of aggregating functions
Adds optional support for conditions in aggregating functions

Updates Readme with example, changes test to use a condition
Adds small note about caching and unsaved cache items
Adds 'required' option to hasOne associations
Stop mysql auto-inserting 0 into owner_id field
Make required false by default
Reflect default hasOne required value change.
Merge pull request #82 from locomote/optional-has-one

Adds 'required' option to hasOne associations
Reindents package.json, adds hat as new dependency for driver uid generation (#86)
Generates an uid for every driver instance (#86)
Changes singleton uid creation to use driver uid (#86)
Changes db.load to avoid lint errors on condition assignment
Changes Readme orm.express example and adds a note about multiple connections
Changes Model.drop and Model.sync to be resistive to no callback
Changes ORM.sync() to also be resistant to no callback
Fixes Readme Express example