Added os.remove(test_file_name) to one of the unit tests.  This failing on Travis and causing some access issues.
Added os.remove(test_file_name) to one of the unit tests.  This failing on Travis and causing some access issues.

PMEAL/OpenPNM,amdouglas/OpenPNM,amdouglas/OpenPNM,TomTranter/OpenPNM,stadelmanma/OpenPNM