Adding GRS 13CO comparison with HCO+

New plots/ directory containing EPS plots of interest from the week.
idl/view_grs_l30.pro is a hacky script to produce plots and do computations.
Updated versions of idl/README.GRS and idl/view_grs_l30.pro
Merge branch 'master' of github.com:BGPS/distance_omnibus2