v1.2.1: Merge pull request #1 from murphygroup/v1.2

Use PyPI package CellSegmentationEvaluator for evaluating segmentations rather than previous local code. Create and use new PyPI package ThreeDCellComposer to enable simple 3D segmentation using deepcell as the 2D segmented.

v1.1

Fixes in
deepcell_only.py:
Modify dimensions of the XZ and YZ to fully pad z with zeros
single_method_eval_3D.py:
Modify KMeans section to avoid doing KMeans with n_clusters=1
Remove saving intermediate binary image file to avoid error in the next run
meshing_3D.py:
Fix output dir and update color map range to 0-1