Further testing of Z136 implementation.

1) Carefully checked values in AnsiZ136MPEDeloriTestInput.txt to make sure they matched what Delori's Excel spreadsheet produces.  They do.

2) Worked through the two cases where there are discrepancies between the PTB code here and the spreadsheet and discovered that the problem is in the value of T2 used.  My reading of the standard is that the PTB code here is correct.  Added comments to this effect in the test code, and added two Word documents that work through the calculations by hand to this repository.  Emailed Delori to see if he has insight about why his spreadsheet uses a different value for T2.

Signed-off-by: David Brainard <brainard@psych.upenn.edu>