Minor fix to PREFIX for S3 bucket.
Minor fix to PREFIX for S3 bucket.

dwhswenson/openpathsampling,jhprinz/openpathsampling,dwhswenson/openpathsampling,choderalab/openpathsampling,dwhswenson/openpathsampling,openpathsampling/openpathsampling,openpathsampling/openpathsampling,choderalab/openpathsampling,openpathsampling/openpathsampling,jhprinz/openpathsampling,jhprinz/openpathsampling,openpathsampling/openpathsampling,choderalab/openpathsampling,dwhswenson/openpathsampling