Adds Python 3 compatible sorting and exception attribute referencing.
Jumble the author names to ensure the sorting logic works.
Packaged.
Revised models to immutable objects and encapsulated OPF parsing.
Module renamed from main to epub
Partial model based representations of content coming out of an epub (and eventually into).
Revises html parsers to accept etree objects rather than epub objects.

This makes the code a bit more reusable as well as makes testing easier.
Revert codebase to use Python 2.7
Forgot to return the URI on success.