System wide virtualenv

It seems like you purposely didn't rely on a system-wide virtualenv so this change might be counter-productive.

I can't think of a reason not to install easy_install, pip, and virtualenv system-wide and I prefer this approach personally.  If easy_install isn't included in the Mac OS X installation then another step will be needed there also.

These changes include pull request #2 but can be easily rebased onto master instead if #2 is rejected.