Pad

Added new pad instruction to match Numpy 1.7.
We don't need 2 classes for this. Only one. So delete the class Pad. Rename PadWithKWargs to pad.

Modify its make_node to have a default value for values of None:

Then in the perform, check if values is None, if so, don't pass a dict. Having less class is good.

Also, you need the infer_shape method. It will probably depend on the shape of array and the value of pad_width.

 def make_node(self, array, pad_width, values=None):

Then, it it is none, but in the graph this variable: theano.tensor.type_others.NoneConst.