Update version of hashdist that we rely on.
Merge pull request #432 from ketch/update_hashdist

Update version of hashdist that we rely on.
Make 3D acoustics tests run faster by using smaller grid.
Make psystem_2d tests run faster by using shorter time and smaller grid.
Modify acoustics 2d variable test to be shorter

Also add specific regression data for classic and sharpclaw.  This was needed
since we now use a much coarser grid.
More description of test parameters.