Several speed & code updates#19

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leopd wants to merge 4 commits intoclcarwin:masterfrom

Commits on Oct 20, 2019

Cleaning up py3 & old torch. Moving bbox functions from numpy to pytorch.
Leo Dirac
committed
Refactoring common "detect" code into its own file, documenting.
Leo Dirac
committed
Made easy to use single method detect_faces, with test.
Leo Dirac
committed

Commits on Oct 21, 2019

Shaved at least 30% off the time for typical face detection.
Leo Dirac
committed