Use the book_reference rather than the copy ID

This is a bit of cruft from the data model - in
the future, the ID should be the book reference.
Stop namespacing the copy resource beneath /books/
Add a new copy view

View for an individual copy of a book
Jump directly to a copy from the start page
Merge pull request #6 from JordanHatch/copy-refactoring

Break out copies into separate pages