Adding a "Creatable" interface.
Updating Contact with the Creatable interface.
Updating E-mail Group with the Creatable interface.
Adding an "Updateable" interface.
Updating Contact with the Updateable interface.
Updating E-mail Subscriptions with the Updateable interface.
Updating E-mail Group with the Updateable interface.
Adding Readable interface to E-mail Group Subscriptions.
Adding a Destroyable interface.
Marking Contacts with Destroyable interface.
Marking E-mail Groups with Destroyable interface.
Fixing typo in Destroyable interface.
Merge pull request #22 from tableau-mkt/crud-interface

Formalize a full CRUD interface.