Minor improvements to submodule test for windows portability
Minor improvements to submodule test for windows portability

However, most tests fail for reasons unknown - SHA cannot be found.

For now, I will wait until someone complains, as I doubt too many people
will use it on windows.

Related to #244

manasdk/GitPython,beni55/GitPython,cdht/GitPython,ghtdak/GitPython,gitpython-developers/GitPython,StyXman/GitPython,StyXman/GitPython,beni55/GitPython,pengshp/GitPython,gitpython-developers/gitpython,gitpython-developers/GitPython,nvie/GitPython,zsjohny/GitPython,avinassh/GitPython,avinassh/GitPython,breavo/GitPython,zsjohny/GitPython,cdht/GitPython,bwrsandman/GitPython,bwrsandman/GitPython,nvie/GitPython,zsjohny/GitPython,gitpython-developers/gitpython,pengshp/GitPython,StyXman/GitPython,expobrain/GitPython,dpursehouse/GitPython,breavo/GitPython,ghtdak/GitPython,dpursehouse/GitPython,jeblair/GitPython,jeblair/GitPython,h4ck3rm1k3/GitPython,avinassh/GitPython,pengshp/GitPython,roidelapluie/GitPython,h4ck3rm1k3/GitPython,roidelapluie/GitPython,expobrain/GitPython,bwrsandman/GitPython,cdht/GitPython,manasdk/GitPython