edited shebang for portability

My understanding is that the shebang should not be a hard call to /usr/bin/python as it will not play nicely with virtual environments and Python installations across different operating systems.  This should make the script more portable

Please see [1, 2] for more info.

[1] http://stackoverflow.com/questions/17846908/proper-shebang-for-python-script
[2] http://stackoverflow.com/questions/5709616/whats-the-difference-between-these-two-python-shebangs