Fix module version detection

* Current implementation of get_version_from_app fails to get version
  information from modules such as ``numpy``, ``webassets`` and ``setuptools`` since
  they define version information in the variable ``<package>.__version__``
  and also include a module ``<package>.version``. In the current
  implementation <package>.version takes precedence over
  ``<package>.__version__`` thus the version information reported is a module
  instead of version number. This is easily fixed by this commit which
  changes precedence (see also PEP396).