Add doc

doc/library/tensor/nnet/conv.txt

@@ -50,6 +50,8 @@ TODO: Give examples for how to use these things! They are pretty complicated.
       <http://deeplearning.net/software/pylearn2/library/linear.html>`_
       implementation.
 
+      Also, there is restrictions on which shape are supported.
+
 .. autofunction:: theano.tensor.nnet.conv.conv2d
 .. autofunction:: theano.tensor.nnet.Conv3D.conv3D
 .. autofunction:: theano.tensor.nnet.conv3d2d.conv3d