Quick and small fixes

[jshuaf]

• Form fields are autofocused when joining a game (fixes #74)
• game.jsx renamed to Game.jsx for git, solving #72
• Prop Types for question sets are exported and imported rather than repeated (fixes #68)
• A loading indicator appears when waiting for response from socket (fixes #69)
• Leftover console statements are removed
• Reducers are cleaned up a bit with combine-reducers function