Add Firefox to run on Travis.
Add Firefox to run on Travis.

egilkh/ngStorage,gsklee/ngStorage,wodka/ngStorage,bratishchev/ngStorage,prudvihemanth/ngStorage,GerryFudd/ngStorage,BaggersIO/ngStorage,lalithr95/ngStorage,wyvern8/ngStorage,robinboehm/ngStorage,imskojs/ngStorage,castle-it/ngStorage,kknirala/ngStorage,JulienBier/ngStorage,4talesa/ngStorage