fixed new interface to liouville classes

classical/newtonian.py

@@ -170,6 +170,7 @@ class Newtonian(Propagator):
 
     def step(self, time, q, p):
         """ perform a time step with initial coordinate and momentum """
-        qt = np.dot(self.ddiffs, self.iln.qobj.get_val_float(q, p))
-        pt = np.dot(self.ddiffs, self.iln.pobj.get_val_float(q, p))
+        qvec, pvec = self.iln.get_val_float(q, p)
+        qt = np.dot(self.ddiffs, qvec)
+        pt = np.dot(self.ddiffs, pvec)
         return (qt, pt)