add masses feature to topology feature
add masses feature to topology feature

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