Changes

Updates README so that I can note that BIT_CHANGING:9ca167aa8b04cbebe4a1177a72f13731454e1e11

Committing a change that will initialize this set of variables
under all circumstances. This change does not affect output
except when the New Hybrid PDF is used. In the case of the
New Hybrid PDF, the variables F_rt, F_thl, F_rt_min, F_rt_max,
F_thl_min, and F_thl_max were never initialized and never set
(they are not part of the New Hybrid PDF -- only in the original
New PDF), resulting NaN values being output to stat files.