Updated response models, added all push notification endpoints. Added new feature called Attributes to access related models as a property on the response model, added typed response models for all default collections.

This includes more polish so all notification endpoints are added and you can send notification to user, users, group, groups, device, devices.
Relationship Attributes so no need to make a 2nd api request to get a default relationship just access the relationship as a property on the response model e.g.: ```$user = Usergrid::users()->findById(['uuid' => '1232']); $device = $user->device;  or $groups = user->groups; ```
This make the the api easier to use.
Also added typed collections for all default collections and when asking a response model for its entities property instead of getting the Base PHP Collection class you now get a typed Collection class so when asking a users response model for its entities I get a Users collection class back.