Bug with grayscale image normalization

[mirandali707]

While running PGAN to produce grayscale output, I think I found a bug in this line -- after the grayscale transform there's only one channel, so Transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)) fails with RuntimeError: output with shape [1, 4, 4] doesn't match the broadcast shape [3, 4, 4]. I fixed this by adding transformList[-1] = Transforms.Normalize([0.5], [0.5]) after line 423.