switch input_sensitivity function to model

GPy/core/model.py

@@ -147,6 +147,12 @@ class Model(Parameterized):
         """
         raise DeprecationWarning, 'parameters now have default constraints'
 
+    def input_sensitivity(self):
+        """
+        Returns the sensitivity for each dimension of this kernel.
+        """
+        return self.kern.input_sensitivity()
+
     def objective_function(self, x):
         """
         The objective function passed to the optimizer. It combines