Update cocaine 0.5.3 -> 0.5.4, minitest 5.3.2 -> 5.3.3

The cocaine gem is a dependency of paperclip. minitest was updated when
I updated cocaine, but I'm not entirely sure why. In any case, these are
both tiny version bumps so I'm not going to worry about it too much.

Change-Id: I6067c7c0728841f5c6e2d5eafac6a5f1287ff284