Try PATH.exe in Windows

This fixes https://github.com/tkf/emacs-jedi/issues/148
Fix python-environment--existing

This causes a bug in Windows.  See:
https://github.com/tkf/emacs-jedi/issues/148
Fix python-environment-bin: Script -> Scripts

Thanks @llcc!
See: https://github.com/tkf/emacs-jedi/issues/148#issuecomment-38285463
Merge branch 'windows-bin'
Fix python-environment-exists-p

Previous version was accidentally working.
Bump to 0.0.2alpha0