Some python package licenses detection issues

As reported by @akaihola in #417
> I am encountering suspicious results with scancode for a few packages which have either heavily modified licenses or have come up with their own license. Some examples:
> - pyproj 1.9.5.1
> - Matplotlib 1.5.3 (licenses of some of the included components, e.g. stix, yorick, pnpoly, bakoma, qhull, agg24)
> - Pillow 3.4.2