Add MediaTypeCollection.member_view.

Signed-off-by: Dane Jensen <dane@rightscale.com>
I would break it into two bullets, the one below and then the one above:
Change: MediaTypeCollection now requires all its views to be explicitly defined (and will not automatically use the underlying member view if it exists). To define a view for member element (wrapping it in a collection) one can use the new `member_view`.