Add mock as a test dependency if running as python2

Test dependencies only get used if running as python setup.py test, so
need to add test_suite
Output correct filenames for documents if version is in the metadata
Exclude the binder in <nav>
Add translucent marker for translucent binders to generated epubs
Change nav items href to be relative
Output the correct title for documents
Fix unicode issues when metadata or content has non ascii characters
Merge pull request #5 from Connexions/fixes

Various fixes