Python 3 compatibility

Removed Unipath dependency as it claims to support Python 3, but has an open
issue regarding Python 3 support <https://github.com/mikeorr/Unipath/pull/10>.

Removed argparse dependency as Python 2.7 and 3.2 included argparse in stdlib.

Furthermore some PEP8 cleanups on the files touched.

Fixes #13