Update notes for 0.5.1

Changelist 0.5.1:
- Fixed: Using modifiers in a match, caused the next match to not start correctly
- Fixed: Using modifiers broke the main menu
- Fixed: Both team's score indicators were reset after each replay
- Fixed: Spawning glitched after replay playback had stopped
- Fixed: Various replay sound glitches
- Fixed: Various graphical glitches