Pending Race Phase 2 Improvements

- Current user data now uses WalkUser.getCurrentUser() data -> Will
need to be improved later when we have a better tie between the
WalkUser.getCurrentUser() and UserStruct models.
- Added in the history ping for when a message is received
- Added in the Button enabling when a new user joins the pending room
* Still needs some work on the state of joining a room that already
exists and seeing the correct people and their states. (Should see all
users tied to that race id, their initial statuses and then any later
updates from the point at which you joined the room)