fix sanitize
changes supplied by Patrick
only email US users about prizes
fix blank lines in email messages
new partial
finishing touches on prizes - stress U.S. only
PR feedback
only show prize providers if prizes are available to be claimed
[Finishes 61915710] fix footer too wide for 900 pixels on mobile issue
hide website references to DonorsChoose until revealed on Monday
localize strings in signup page
Merge pull request #188 from code-dot-org/prize_finishing_touches

Prize finishing touches