No change to tests themselves. Regression testing for ifu_3d_collapse().
No change to ifu_math(). Optimized collapse routine in ifu_3d_collapse() and several bug fixes in sigma clipping routine. Continued testing of sigma clipping option.
Conversion of Nans to 0s in Eagle Nebula datacube to fix runtime errors in ifu_3d_collapse() w/ sigma clipping turned on.
Bugs squashed mainly in ifu_3d_collapse(). See tests/ commit messages for details.