IMPORTANT: run `npm update` to install `firebase` & `reactfire` libraries

`src/script/screen/chat.jsx`: new screen

`gulpfile.js`, `package.json`: added new `firebase` & `reactfire` libraries

`app.jsx`: `handleChatChange`; new argument for `handleProfileChange` to identify when viewing a profile that the user matched with

`userListItemCompact.jsx`, `activity.jsx`: minor, to support identifying which users we've matched with

`remote.js`: bug fix, "Matches" was not filtering correctly

`profile.jsx`: show "Chat" button when viewing a profile that the user matched with

`app.scss`: CSS for new `Chat` screen