Port updated write_version_py from mdtraj
Port updated write_version_py from mdtraj

mpharrigan/mixtape,msultan/msmbuilder,mpharrigan/mixtape,rafwiewiora/msmbuilder,Eigenstate/msmbuilder,rafwiewiora/msmbuilder,Eigenstate/msmbuilder,rafwiewiora/msmbuilder,cxhernandez/msmbuilder,brookehus/msmbuilder,dr-nate/msmbuilder,msultan/msmbuilder,dr-nate/msmbuilder,msmbuilder/msmbuilder,brookehus/msmbuilder,Eigenstate/msmbuilder,msultan/msmbuilder,peastman/msmbuilder,rafwiewiora/msmbuilder,msmbuilder/msmbuilder,dr-nate/msmbuilder,msultan/msmbuilder,brookehus/msmbuilder,peastman/msmbuilder,msmbuilder/msmbuilder,cxhernandez/msmbuilder,mpharrigan/mixtape,peastman/msmbuilder,rafwiewiora/msmbuilder,Eigenstate/msmbuilder,msmbuilder/msmbuilder,Eigenstate/msmbuilder,mpharrigan/mixtape,dr-nate/msmbuilder,cxhernandez/msmbuilder,mpharrigan/mixtape,msultan/msmbuilder,peastman/msmbuilder,brookehus/msmbuilder,cxhernandez/msmbuilder,msmbuilder/msmbuilder,brookehus/msmbuilder,dr-nate/msmbuilder,cxhernandez/msmbuilder,peastman/msmbuilder