MAINT: ma: clean up ma/test_extras.py: don't use 'import *'; PEP8 whitespace
BUG: ma: ma.average didn't handle complex arrays correctly (issue gh-2684)
Merge pull request #3440 from WarrenWeckesser/bug-ma-average

BUG: ma: ma.average didn't handle complex arrays correctly (issue gh-2684)