Improve community_louvain function

[akimbler]

The description for the community_louvain function is misleading. It is supposed to improve upon and subsume the roles of the modularity_louvain_xxx functions. It does not, however, accept signed connection matrices, so it fails to subsume the signed functions. Resulting in a lot of redundant code and the need for modularity_louvain_xxx_sign functions to still exists.

TL:DR, community_louvain needs to be made to work with signed input