Standard testing of mstats vs. stats results

I implemented a test class which allows unittesting the results between stats and mstats.
This work originated from the following this issue (https://github.com/scipy/scipy/issues/2318).

What you can do:
a) compare stats and mstats results in a consistent manner
b) print a table which gives you an overview about the routines which have already unittests implemented (use print_stats_mstats_comparison for this)

Results of the unittests indicate that for some routines in mstats there are bugs. I have initially commented these tests in the code, so the tests run properly through.

Next step would be to actually look, where and why these differences fail. I therefore propose to create new issues for these bugs/inconsistencies to keep the actual test setup separate from potential code bugfixes