Delete old Seasonals and unused suspect test formats
Make PU the new Other Metagame of the Month.
Tier Shift remains as a playable Other Metagame.
Add new Seasonal Ladder, May Mayhem.
Add Gen 1 OU Beta ladder.
Merge branch 'format-changes' of https://github.com/Joimer/Pokemon-Showdown

Update OM of the month, add new Seasonal, add Gen 1 ladder
Fix logic error in May seasonal