v0.7.0

Breaking Change

• renamed the changed method to modelChanges #32

Where before you would do this to see model changes:

 let user = store.peekRecord('user', 1);
 user.set('name', 'Zippy');
 user.changed(); //=> { name: ['Bob', 'Zippy']}

You would now do this:

 let user = store.peekRecord('user', 1);
 user.set('name', 'Zippy');
 user.modelChanges(); //=> { name: ['Bob', 'Zippy']}