guess-player-levels: improved tooltip

- include player nickname (in case the nickname is too long to be fully visible)
- use level colors (similar to the player tracker tooltip)
doh! daft bug
fixes #705
Merge pull request #706 from fkloft/guess-player-levels

guess-player-levels: improved tooltip
digital bumper sticker: fix so it doesn't cause JS errors when IITC is running