add cluster method to adjacency class

[ljchang]

It would be nice to have any type of clustering from sklearn implemented, especially for clustering graphs.

[jeremymanning]

This might be useful: http://hypertools.readthedocs.io/en/latest/hypertools.cluster.html#hypertools.cluster

[ljchang]

oh, nice that's perfect! I'll just have to add some checks if it is a distance or similarity matrix.