[tests] Added hhvm-nightly to travis builds
[tests] Added hhvm-nightly to travis builds

zjien/Ratchet,vinod1988/Ratchet,IRlyDontKnow/Ratchet,krageon/Ratchet,cesarmarinhorj/Ratchet,b-viguier/Ratchet,KSDaemon/Ratchet,mbonneau/Ratchet,sudarshan955/Ratchet,ratchetphp/Ratchet,Nek-/Ratchet,Jumplead/Ratchet,ctkjose/Ratchet,naroga/Ratchet