Re-implement elpa-get using Python and elisp

site-start.el saves the location of it to virtualenv-site-lisp so
that elpa-get does not need to know $VIRTUAL_ENV.
Fix: load-path should not end with slash

It seems this is why site-lisp/elpa was not included in the load-path
and thus the test failed.
Do not add virtualenv-emacs to tox.ini:dpes

tox automatically install the current project.  Previously elpa-get
was not installed because of this.
Add --reinstall option to force installation
Merge pull request #4 from tkf/virtualenv-site-lisp

Avoid reinstalling packages by elpa-get