Merge pull request #3 from daniel-dgi/7.x

Updating code to match changes made to 7.x core functionality.  Don't merge this until UCLA gives their demo on 14/12/2012
Access callback now uses the datastream access callback from islandora core in addition to module specific checks.
Merge branch '7.x' of https://github.com/discoverygarden/ucla_pdf into 7.x