Python 3 support

[jkfurtney]

This module currently only works in Python 2. Converting to Python 3 should be relatively easy. But, given the byte manipulation code, simultaneously supporting Python 2 and 3 could be difficult.

Long term Itasca is transitioning to Python 3.

Maybe we can leave an old Python 2 comparable version on pyPI and release Python 3 version.

Should we drop support for the FLAC3D_Connection, PFC3D_Connection and 3DEC_Connection classes since these codes all have Python now and can use the better p2pLinkClient/p2pLinkServer classes?