changed hitoriplot to center numbers in each square, turned off axis labels
added the timeit library from http://www.mathworks.com/matlabcentral/fileexchange/18798-timeit-benchmarking-function by Steve Eddins for benchmarking the solver
fixed a bug where, in the final row, if the solution didn't validate column-wise, the last row was not removed, leading to a solution with too many rows.  commented out throwing an error when the hitori is solved so that benchmarking can complete.  added a couple more puzzles and a benchmarking example in usage.m