specify ZeroDivisionError
Merge remote-tracking branch 'zaki/master'
brought over three changes from zaki (4 group check, zero weight error catch, and group bias fix)
Refreshing common pspec scripts.
- Anything with dubious providence is moved to old
- pspec_redmult_cov_gps.py is a merge of danny and zaki
adding danny's simple pspec shell script