Add getRelationValue method
Move Hashable usage to explicit trait
Tidy up
Sluggable traits must now be used in the Model class definition.
Purgeable traits must now be used in the Model class definition.
Add priority to event emitter
Validation traits must now be used in the Model class definition
We no longer need to boot local traits
Fixes conflicts where traits are used in base classes
Adds helper method to validation trait: isAttributeRequired
Remove dependancy on purgeable
Fix bugs in Hashable