Remove all parametric test machinery, which is super fragile.

Also, turn empty module exceptions into a function call so we can
gradually refactor that out and allow for empty modules.
First changes towards allowing empty modules to appear during
modularity updates.

The empty modules will be allowed without raising an exception,
instead they will be immediately removed with a renaming of the
remaining labels.
Ensure test compares sorted lists.
Merge pull request #3 from fperez/empty-modules

Remove old parametric testing from test suite, add functionality for dealing with empty partitions in modularity.py