Added JensenShannon distance function with test
started adding KolmorgorovSmirnoff
Fixed check for zero probability value in JensenShannon and updated test.
Corrected comment for Jensen-Shannon.
Next set of changes to ks
Fixed typo in JensenShannon comment
Merge pull request #8 from gonum/feature-js

Added JensenShannon distance function with test
merged in with master
Added Kolmogorov-Smirnov distance function and test