Updated travis setup script to not install extensions with the hhvm system.
Updated travis setup script to not install extensions with the hhvm system.

alawnchen/Stash,AndrewCarterUK/Stash,csburton/Stash,localheinz/Stash,localheinz/Stash,andrerom/Stash,alawnchen/Stash,csburton/Stash,AndrewCarterUK/Stash,jaredtking/Stash,theUniC/Stash,bankiru/Stash,tedious/Stash,theUniC/Stash,graphis/Stash,jaredtking/Stash,graphis/Stash,andrerom/Stash,tedious/Stash,bankiru/Stash