MAINT: remove numpy.matrix usage from linalg.matfuncs.py code and enable expm of more array_likes
Merge pull request #3308 from argriffing/remove-some-mats

MAINT: linalg: code cleanups in matfuncs

Remove numpy.matrix usage from linalg.matfuncs.py code and enable expm of more array_likes.
Also misc code cleanups.