Merging Runs 12 and 13 for A_LL

fms meeting 11.16.17
procedure merging runs 12 and 13 asymmetries and errors

spin meeting 11.27.17
updated purity fits, paper status update, discussion of mass distribution figure(s)

fms meeting 11.30.17
pT rebin; updated final polarizations (and 12+13 merge) and luminosities