Update rummageable so it allows "subsubsection" key in search index.
Update rummageable so it allows "subsubsection" key in search index.

See de3ac6a516376c105c64940d91326e86d6b75407 for details.

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