Remove unused getEpub3Toc method
Merge branch 'develop' into feature/epub-module-refactoring
Remove unused bindings-related Backbone models.
Use metadata directly from plain JSON instead of through a Backbone model.
Rename function argument for a more descriptive name.
Remove unused methods from spine item Backbone model.
Remove unused methods and Backbone models from the epub module.
Manifest refactoring:

* Use plain JavaScript prototype instead of a Backbone model,
* Indexed lookup of manifest items for better performance,
* Placing fanifest-related methods in the manifest prototype,
* Removal of unused source files.
Merge pull request #35 from readium/feature/epub-module-refactoring

Remove unused getEpub3Toc method