Handle JSON data on member create and update.
Handle JSON data on member create and update.

Added `RESTfulView._get_data()`, which inspects the content-type header to determine how to decode POST data. Currently, encoded form data and JSON content are supported.

Updated `create_member` and `update_member` views to use `_get_data` so that they can handle JSON submissions.

XXX: Should the view decode data directly or ask the model to do it?

wylee/pyramid_restler