Add Hommola cospeciation test

Here, we have added a statistical test for host:parasite cospeciation derived from Hommola et al (2009, Molecular Biology and Evolution). This is added as a new module called evolve under math.stats.

We are looking for feedback on the organization and naming of the evolve module. We're not quite sure what to add to the top level description for this module, so any other ideas would be appreciated. 

Note: the test itself is using numpy arrays rather than distance matrix objects because we are using the positional relationships between host, parasite, and an interaction matrix rather than the labels. 
I'm honestly not sure of the best way to deal with this, and you're right that it likely affects other permutation-based methods (e.g., Mantel). Performance-wise, sorting the data for each permutation seems a little scary...

Another (potentially quicker) option would be to truncate each correlation coefficient to some number of decimal places before doing the comparison, though I don't know if this is a valid solution either.

What are the p-values that you get with and without your sorting fix, using 999 permutations with the paper's test dataset? What p-value do you get from the author's R code?