Trick to remove checkerboard artifacts

[krisrs1128]

In some of the images on the 500-image subsample we can see checkerboard patterns. We could remove them using this trick.

Not as high a priority as getting generated images across all images / just seeing if it goes away after enough iterations. But could potentially lead to better images faster.

[krisrs1128]

Alternatively, try increasing lambda_gan to see if that forces the artifacts to go away (these were trained with lambda_L = 1 and lambda_gan = 0.001).

[krisrs1128]

Closed by #138. We'll see if it actually improves training.