Remove RVM from build script.
Remove RVM from build script.

robinwhittleton/whitehall,alphagov/whitehall,hotvulcan/whitehall,hotvulcan/whitehall,ggoral/whitehall,hotvulcan/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,robinwhittleton/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,robinwhittleton/whitehall,ggoral/whitehall,ggoral/whitehall,hotvulcan/whitehall,askl56/whitehall,robinwhittleton/whitehall,alphagov/whitehall