improved cache, read and write for OP
improved cache, read and write for OP

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