fix numpy int index bug
fix numpy int index bug

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