Update version requirements to allow pyparsing 2.0.1 for py 2.6,2.7

According to http://pyparsing.wikispaces.com/ the latest version 2.0.1 of pyparsing will work with python 2.6 and 2.7.  This updates the setup.py requirements accordingly.  There is an odd requirement for python 2.6 and 2.7 of allowing any version *except* 2.0.0.