Ported to Python3.2 mostly via 2to3 tool.

This work was performed by Tejashri Kandolkar and Sandeep Shelke.
Merge https://github.com/gravenimage/mplstereonet into python3-support

Conflicts:
	mplstereonet/__init__.py
	mplstereonet/contouring.py
Removed unnecessary `list` calls from 2to3
Changes to testing infrastructure for python3
Changes to examples for python3 compatibility
Fix mistaken threshold value in image comparison that crept in somewhere