no sandbox.cuda #109

Hi
following the Guided Backpropagation recipe/example I had error for:
if theano.sandbox.cuda.cuda_enabled because, I guess, I use newer theano / lasagne versions with CuDNN etc. I have no cuda under theano.sandbox. two solutions:

1. skip the if and use the else option: maybe_to_gpu = lambda x: x
2. use gpu with gpuarray.dnn
   maybe_to_gpu = theano.gpuarray.dnn.as_gpuarray_variable x = maybe_to_gpu(x,None)
   and then a few lines below (as above, add None as second input argument):
   outp = maybe_to_gpu(self.nonlinearity(inp),None)
   Thanks for the examples