Refactoring/debugging/optimizing of motion correction.
Merge branch '3D_SIMA' of github.com:losonczylab/sima into 3D_SIMA
Bug fix.
work on 3D ROI.  Everything seems to be working (poly2mask, mask2poly, etc.) and inverting appropriately.

Might want to re-visit some of the (x,y,z) vs. (z,y,x) conventions as well as cases in which user passes in 2D polygons or mask to ensure behavior is intuitive
Merge branch '3D_SIMA' of github.com:losonczylab/sima into 3D_SIMA
work on 3D ROI class
ROI class initialization and all class methods updated for 3D
added warning statements to make behavior more explicit
ROIList transform adapted to 3D
cleanup
Rewrote _frame_alignment_correlation to parallelize the main correlation calculation.