New class: Sharpshooter! + bugfix and balances

- Added new class: 'Sharpshooter'.
- Added skill: 'Sniper'.
- Added skill: 'Ballistra'.
- Added 'Exploding Chickens' powerup.
- Added some tooltip texts.
- Added rotation animation to Snowball.
- Added '25 Gold' item.
- Added 'Dark Mastery' powerup.
- Added 'Holy Mastery' powerup.
- Fixed 'IO' sprite origin to be more centered.
- Fixed 'Witch' sprite origin to be more centered.
- Fixed 'Knight' sprite origin to be more centered.
- Fixed item pickup range when player is bigger.
- Increased 'Fire Dash' damage.
- Increased 'Zap' damage.
- Increased 'Bolas' damage.
- Changed IO death voice.
- Spawn less 'Gelatinous Cube' in 'The Climb'.
- Spawn 'Mimic' slightly more.
- Fixed free gems bug.
- Removed 'Balls of Steel' from tough guy.
- Made speed in Bestiary more readable.