Fix aspect ratio jitter
Fix aspect ratio jitter

Previously, the aspect ratio was sampled from [(3/4)^2, (4/3)^2] instead
of [3/4, 4/3]. Thanks to Kaiming for pointing out the bug.

This does not seem to have much of an effect on accuracy.

ltrottier/pelu.resnet.torch,ltrottier/pelu.resnet.torch