Update README.md

README.md

-[pymolfile]
+pymolfile
+
+Usage example:
+
+import pymolfile
+
+molfile = pymolfile.OpenMolfile('test/ala3.pdb')
+
+print(molfile.topology.structure)
+print(molfile.topology.bonds)
+print(molfile.topology.angles)
+
+molfile_traj = molfile.trajectory.iread()
+