Python: `cd` option problems.

[seriyps]

Looks like cd option introduce some problems:

1> PyBaseDir = "/home/seriy/workspace/mediamon_crawl/priv/py_trash_filter",
1> Virtualenv = PyBaseDir ++ "/pyenv",
1> Python = Virtualenv ++ "/bin/python2.7".
2> python:start([{env, [{"VIRTUAL_ENV", Virtualenv}]},
                 {python, Python},
                 {python_path, [PyBaseDir]}]).
{ok,<0.355.0>}
3> python:start([{env, [{"VIRTUAL_ENV", Virtualenv}]},
                 {python, Python},
                 {python_path, [PyBaseDir]},
                 {cd, PyBaseDir}]).
{ok,<0.357.0>}
/home/seriy/workspace/mediamon_crawl/priv/py_trash_filter/pyenv/bin/python2.7: No module named erlport

Looks like this is because https://github.com/hdima/erlport/blob/1.0.0alpha/src/python_options.erl#L119 generate relative path. Maybe wrap it with filemane:absname/1?