Imporved installation instructions for Mac OSX
Removed parallelization in cython because it was slower.
Improved robustness to case of constant intensity frame.
Masking of displacements with poor correlations in frame align.
Partial.
3D HMM calls frame_alignment with correlation criterion
Fix to correlation thresholding in frame alignment
Ignore masked frames in whole frame shifting
Fixes to 3D HMM and removal of itertool.chain(*
Bug fix.