Corrected a README example
Corrected a README example


Former-commit-id: 86993e6ad88763573c9a4e725d9163e154e4d169
openworm/PyOpenWorm,hnunner/PyOpenWorm,kaustubhcs/PyOpenWorm,openworm/PyOpenWorm,travs/PyOpenWorm,gsarma/PyOpenWorm,gsarma/PyOpenWorm