Update firebase to the latest version 🚀 #12

greenkeeper[bot] wants to merge 2 commits intomaster the-road-to-react-with-firebase/react-semantic-ui-firebase-authentication:masterfrom

greenkeeper/firebase-6.0.0 the-road-to-react-with-firebase/react-semantic-ui-firebase-authentication:greenkeeper/firebase-6.0.0Copy head branch name to clipboard