Upgrade requirement to pyparsing 2.0.1

The newly released pyparsing 2.0.1 fixes a number of problems with supporting Python 2.x and 3.x at the same time.  Unfortunately, I think the ship has sailed to get this in for 1.3.0, but for 1.3.1 we should be able to do this.

http://code.activestate.com/lists/python-list/647675/