`swipe-stack-0.1.js`: Adding pause/unpause (won't respond to drags when paused)

`app.jsx`: adding `Welcome2Screen`

`welcome2.jsx`: new screen

`userListItem.jsx`: Making `pubSub.publish('heroes.toggleButtons')` more specific (not actually a toggle anymore, really)

`heroes.jsx`: Adding drag pause; better toggleButton;

`app.scss`: Slight CSS tweak to buttons in top position