Prework Milestone 4: Viewing all players

**Problem:** 
I want to be able to see other players moving around. 

**Implementation Suggestions:**
Blocked first by #8, #9 and #10 but once we have our game client described in the README with the map, our personal avatar and movement, we should also be able to display other player's avatars. 

**Testing Criteria:** 
Open index.html in Chrome and confirm that we can see other avatars moving