Documentation should build and test under python 3.x

Currently the documentation either can't build, can't test, or both under python 3.x. In the v2.9 branch the source needs to run through 2to3 before the docs are built. In v2.9 and master the documentation has to be updated to be python 3.x compatible. This mostly appears to involve changing lines like:

print foo

to

print(foo)