Add a better string reprensentation of Tile.

theano/tensor/basic.py

@@ -3999,6 +3999,9 @@ class Tile(Op):
     def __hash__(self):
         return hash(Tile) ^ hash(self.ndim)
 
+    def __str__(self):
+        return self.__class__.__name__ + "{ndim=%d}" % self.ndim
+
     def make_node(self, x, reps):
         x = as_tensor_variable(x)
         reps = as_tensor_variable(reps)