Contribute with clustering algorithm

[seoanezonjic]

Hi @GiulioRossetti I have been using CDLIB for several years and it's my first option when I have to clusterize a network. CDlib is a great tool and I hope to use it for many years. Rigth now, I'm working with large networks and I was interested to apply the HLC algorithm due to the necessities of my project. My problems are:

• HLC implemented in CDLIB cannot handle weigths (but the picked implementation has code for it and I have activate it)
• HLC no implements the exact description of Ahn et al
• The implementation it's not optimized for large networks.

Due to these problems, I have forked cdlib and implemented additional HLC in the following ways:

• HLC_w: Activates weighted networks in cdlib's original code
• HLC_f: New implementation that handles binary and weighted networks using numpy and scipy . It's a lot faster that original implementation and follows the Ahn's paper description.

The code is here . I want to contribute to CDLIB but I'm not sure how to make a correct pull request. Thank you in advance Pedro Seoane

[GiulioRossetti]

Thanks for the contribution! I generated the PR #240 - as soon as the test are ok I'll proceed with the integration in the master branch.

Best, Giulio