Add a parsing hook for Model
Add custom parsing to Contact to allow extras to be given as 'extras-foo'
Change DummyApi to return extras the same way the real api does
Change Contact.do.parse() to also handle 'subscription-' options
Change DummyContactsResource to return subscriptions the same way the real api does
Better name for the helper method on Contact for grouping the extra and subscription attributes into an object
Merge branch 'feature/issue-141-handle-the-fact-the-way-we-obtain-extras' into develop