Fix wonky WorldPay form loading

Originally the form would appear to the right of the page instead
of to the left. This was caused by late application of the CSS.

Adding the worldpay module to the head of the document prevents
this problem.

Change-Id: I7657e6c7070d3c9b45ddd6be12f1b8f9d33ec861
Merge "Fix wonky WorldPay form loading"