Throw errors when you fail to create and update with a bang! Return booleans on create and update when not banging.
Ensure callbacks are run on banged methods as well as rescued ones. Return boolean value on `save` and `update`, and return `self` on `create` as ActiveRecord does.
Merge pull request #88 from llhupp/bang_better

Throw errors when you fail to create and update with a bang!