Fix Travis
Fix Travis

Add `npm install node-sass` separately, as
that tends to cause issues.

jeremiahyan/codecombat,codecombat/codecombat,codecombat/codecombat,jeremiahyan/codecombat,javatlacati/codecombat,codecombat/codecombat,jeremiahyan/codecombat,javatlacati/codecombat,kidaa/codecombat,jeremiahyan/codecombat,kidaa/codecombat,codecombat/codecombat,javatlacati/codecombat,codecombat/codecombat,kidaa/codecombat,kidaa/codecombat,javatlacati/codecombat,javatlacati/codecombat