Swap before and after image placement for snapshots
Swap before and after image placement for snapshots

The before image should appear on the left and the after image should
appear on the right. This matches our left-to-right reading style and
also what we often see in code review tools.

Closes #16

Change-Id: I7c90f6102017e3be47325579b2da7cdfd04206f0

diffux/diffux,diffux/diffux,diffux/diffux,kalw/diffux,kalw/diffux,kalw/diffux