An IDL routine to combine measurements

It corrects for over-dispersion to account for possible underestimations of individual measurements, as well as an intrinsically varying physical quantity. The routine does not correct for under-dispersion to avoid strange behaviours in cases where individual measurements are very close one to another.

This IDL routines uses the method described here (en.wikipedia.org/wiki/Weighted_arithmetic_mean#Correcting_for_over-_or_under-dispersion), and was used to combine radial velocity, proper motion and distance measurements in Gagné et al. (2014).