HPT-229 Page Turner functionality

This pull request contains a fairly large number of changes and additions. The most noteworthy being:

Controller action to translate a given page number into the location of an image datastream for that page
Addition of the Internet Archive BookReader Javascript code and related pieces
A page and partials for the BookReader to launch in
New routes to support controller actions and launching the reader for a given Paged item
Links to the BookReader in the Paged views
A score exemplar that can be loaded as a factory for testing
A rake task to load the score using the factory and it's images from fixtures