Add support for AnalysisBaseExternals Python 2.7 and Python 3 in same environment (!29)
Resolves #4 (closed)
Unset PYTHONHOME and PYTHONPATH and add supporting Python .pth file
As PYTHONHOME and PYTHONPATH are unset then a AnalysisBaseExternals_python2.pth file needs to be added for the AnalysisBase Externals Python 2.7 to be used along with ROOT in the same environment as Python 3
Edited by Matthew Feickert