#73: sideboard now just runs out of one big virtualenv

This ended up being pretty straightforward, even including documentation updates.

Everything basically works exactly the same.  There are some moderate performance benefits at startup, mostly when running ``py.test``.

The MAGFest code is working fine with the new system with no changes needed, which is a good sign.
For some reason, Python 3.2 was consistently timing out and all of the other environments have been working.  Since I don't think we'll literally every have a single person who needs to use Python 3.2, I just turned it off.