Add documentation for using underscored API endpoings and underscored root objects in JSON responses.

Starting in Beta 1 the RESTAdapter tries to send API requests to '/blog-posts' instead of '/blog_posts' as it had done previously.  It also expects the root object of a JSON response to be camelized instead of underscored.  This PR add info to the TRANSITION document about how to go back to the previous functionality.
Merge pull request #1241 from jagthedrummer/jeremy/api-endpoint-transition

Add info for using underscored API endpoints and JSON root objects