Get access to the epub model

Included is a pull request for the following:
1. Clean up one of the rvmrc warnings we were getting
2. Get access to the epub model as we had in the previous version.

For 2, we need this in order to figure out spine item information. We then use this information to navigate to pages via openSpineItemElementCfi. Newer updates of readium have broken this functionality.

-Terry, Tim, Lenny, and the rest of the Versapub team