Metrics should be part of PolyMath

[olekscode]

Cosine similarity, euclidean distance - these things are not limited to NLP. So they should be in PolyMath. And people who use Polyglot can install PolyMath if they need metrics

[nikhilpinnaparaju]

Sure, I can go ahead and add these to PolyMath but installing all of such a large package just for a few simple methods seems a little overkill.