Cleanup

I installed virtualenvwrapper-win on my setup of Python 3.3 and virtualenv 1.9.1 and found most of the commands not really working at all.

I'm guessing checking for the PYTHONHOME env variable used to be the thing to look out for as I saw it used in most of the scripts? I changed them to use VIRTUAL_ENV instead and it seems to work now for me.

I also changed the mkvirtualenv.bat a bit so it'll pass on any extra arguments properly to virtualenv.