Running from within a virtualenv

I wanted to use `tox --current-env` from within a *virtualenv*. I could not find anything in the README indicating that it doesn't fundamentally work.

However, since tox-current-env just symlinks the `python` executable of the virtualenv, the normal mechanism of virtualenv to set `sys.path` relative to the path of the python executable does not seem to apply and none of the site-packages of the virtualenv are available in `tox-current-env`'s fake virtualenv.

I'm wondering if this is intentional, then maybe the documentation could be improved. Otherwise maybe symlink the `lib` directory of the virtualenv or possibly setting `PYTHONPATH` could help such that tox-current-env also works out of a virtualenv.