Add --quiet option by default for Windows

Otherwise virtualenv raises UnicodeEncodeError
See: https://github.com/tkf/emacs-jedi/issues/148#issuecomment-38290546
Add --verbose when python-environment--verbose is t
Merge pull request #9 from tkf/virtualenv--quiet-for-windows

This is something I forgot to do in #8 for
https://github.com/tkf/emacs-jedi/issues/148