mount Celeste root dir in GalSim Vagrant VM
mount Celeste root dir in GalSim Vagrant VM

this makes it easy to reference catalogs generated under `benchmark/accuracy/output` when running
the GalSim field generation script, `benchmark/galsim/galsim_field.py`

jeff-regier/Celeste.jl,jeff-regier/Celeste.jl,jeff-regier/Celeste.jl