virtualenv-permissions: Allow www-data to access all venv modules files

To solve:

```
root@ip-10-76-205-185:/opt/wwc/log# # From /etc/init/lms-xml.conf
root@ip-10-76-205-185:/opt/wwc/log# su www-data
$ bash
www-data@ip-10-76-205-185:/mnt/logs$ /opt/edx/bin/gunicorn --preload -b 127.0.0.1:8030 -w 2 --timeout=300 --pythonpath=/opt/wwc/edx-platform  lms.wsgi
Traceback (most recent call last):
  File "/opt/edx/bin/gunicorn", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2897, in <module>
    add_activation_listener(lambda dist: dist.activate())
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 712, in subscribe
    callback(dist)
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2897, in <lambda>
    add_activation_listener(lambda dist: dist.activate())
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2329, in activate
    self.insert_on(path)
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2436, in insert_on
    self.check_version_conflict()
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2475, in check_version_conflict
    for modname in self._get_metadata('top_level.txt'):
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 2323, in _get_metadata
    for line in self.get_metadata_lines(name):
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 1246, in get_metadata_lines
    return yield_lines(self.get_metadata(name))
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 1238, in get_metadata
    return self._get(self._fn(self.egg_info,name))
  File "/opt/edx/local/lib/python2.7/site-packages/pkg_resources.py", line 1353, in _get
    stream = open(path, 'rb')
IOError: [Errno 13] Permission denied: '/opt/edx/lib/python2.7/site-packages/httplib2-0.8-py2.7.egg-info/top_level.txt'
```