Revisit M=6.5 epi/alea uncertainty cutoff

[pmpowers-usgs]

Migrated from usgs/nshm-cous-2014#26

Revisit brange.3dip.gr.xml which throws warning and epi branch has no mags, but does not qualify for m<6.5 suppression of all epistemic uncertainty
dMag = 0.14
mMin = 6.5 --> 6.57 (min bin center)
mMax = 6.78 --> 6.71 (max bin center)

mMax - 0.2 = 6.51

Related question: When bins in gridded sources are capped (to avoid double counting) are they capped at a magnitude that considers uncertainty (M - epiDelta)?