Fix #410 Score headers with explicit ordering not aligning

Fix https://github.com/codalab/codalab/issues/410.

Rendering headers and values is based on two different structures that maintain the same order when the competition does not specify an explicit order. One fix would be to change the API to return the same ordering for these two structures in all cases; however, since they are different structures, it is harder to enforce this peculiarity. Therefore, the proposed fix is to render headers and score values using the same order, the headers order.