Add info on sending underscored JSON for create/update operations

In 0.13 the REST Adapter would send underscored JSON for create/update
requests.  Beginning in Beta 1 the REST Adapter sends camelized JSON.

This PR updates TRANSISTION.md to show how to get back to underscores.
Merge branch 'jeremy/underscore-json-serializer' of https://github.com/jagthedrummer/data into jagthedrummer-jeremy/underscore-json-serializer

Conflicts:
	TRANSITION.md