"adjust" kwarg missing in ewmcorr, ewmstd etc.
In 8.1, the  "adjust" argument was added to pandas.moments.ewma, but not to ewmcorr, ewmcov, ewmstd, ewmvar, ewmvol Their  doc string says all of them have the option to pass adjust, but that's not the case. It's a trivial change & I'll try to submit a pull request to fix it if I find the time.

discussion
https://groups.google.com/forum/#!topic/pystatsmodels/9VvSpp_h8uo
