BUG: Prevent abuse of kwargs in stat functions
Addresses issue #12301 by filtering `kwargs` argument in stat functions to prevent the passage of clearly invalid arguments while at the same time maintaining compatibility with analogous `numpy` functions.

Suggestions on where I could place tests to make sure such an issue doesn't crop up again?  Tried finding a place, but no one place really stood out to me.
 tests/frame/test_analytics.py
 or maybe better in test_generic.py (if you place it in Generic then it will be run for each of the structures)
 @jreback : Off topic, but I noticed that there's a MASSIVE queue on Travis right now.  There seem to be a ton of duplicate builds that could be cancelled.
 its actually progressing, travis was down most of today. 
 your builds occur independently of pandas FYI
 Ah, I see.  Also, I like the suggestion for `test_generic.py`.  I'll go with that one.
 lgtm. ping when green.
 pls add a whatsnew entry (you can put in API changes)
 @jreback : Travis is happy again.  Good to merge if there's nothing else.
