The implementation of similarity(MatrixRow a, MatrixRow b) has been made faster now because the while loop does no longer have to store the columns two times in the variable.
fixed the case when one of the vectors has length 0!
Fix for one of the vectors with length 0 (2). I have run the tests and they show no errors.
Merge pull request #191 from Alan502/fast-matrix

The implementation of similarity(MatrixRow a, MatrixRow b) has been made faster now because the while loop does no longer have to store the columns two times in the variable.