Updated Backbone.Validations to work with the new Backbone validation style:

- Re-use & extend the default Backbone.validate function instead of re-implementing
- Raise 'invalid' events on error as 'error' is reserved for xhr errors
- 'error' callback is not called on validation errors
- To get validation to fire on 'set', call with {validate: true} in unit tests
Merge pull request #34 from spmason/backbone-0.9.10

Updated Backbone.Validations to work with Backbone 0.9.10