Link prediction algorithms

I tried to implement some simple link prediction algorithms which I am going to use in my work. There are only two algorithms that I have implemented: common neighbors and resource allocation index. Complete list of well-known algorithms can be found [here](http://arxiv.org/pdf/1010.0725v1.pdf). Some link prediction algorithms based on cluster information are emerging recently ([here](http://dl.acm.org/citation.cfm?id=2187980.2188150&coll=DL&dl=ACM) and [here](http://link.springer.com/chapter/10.1007%2F978-3-642-34459-6_10)) so I am thinking of implementing some of them too.

This request is NOT ready to be merged. Many improvements are still needed. Please let me know if you're interested by leaving any comments.