WENO flux contains bug

Output from WENO flux is an order of magnitude larger than expected, and expected output seems reasonable here.

Sample failure (from case (b)) -- a is WENO flux output, b is expected output:

a = array([ -151.75264,   419.04852,   274.21088,   274.21088, -1628.2146 ], dtype=float32),
b = array([ -4.35371 ,  12.247949,   8.995223,   8.995223, -51.390392], dtype=float32)