[SciPy-Dev] contribute wald-wolfowitz runs test to scipy.stats

Hi, I wrote a bit of code that computes the test statistic and p-value for the wald-wolfowitz runs test. Seems like it would fit nicely alongside the other statistical tests in the stats module (ansari, bartlett, ...). The code is currently available here <https://github.com/parkus/mypy/blob/master/statsutils.py> -- the function named runstest. The code works for my purposes, but I expect there is still much to be done before it will be ready for a pull request. Per the guide on contributing to SciPy, I figured I would get the conversation started to find out whether the community thought it a worthwhile contribution before making the effort to get it ready for a PR. Best, Parke