Version 0.1.3 RELEASED - Shield powerup, Air Dash tuning, and more

Release notes: [list] [*] [b]Powerup - Shield (NEW):[/b] Grabbing this powerup will give you an instant 10-second immunity from all projectile attacks. [*] [b]Powerup - Health:[/b] Now divides your knockback damage in half. (Previously subtracted your knockback by a flat rate of 60%.) [*] [b]Air dash:[/b] Changed buttons to activate "air dash" in twinstick controls. Now activated by single-tapping the top bumpers. Double-tapping the left joystick is still active, and air dash for bumper controls are unchanged. [i](EDIT: It appears that the change to the twinstick air dash did cause some problems for the bumper controls. This will be fixed in the next update.)[/i] [*] [b]Sound effects:[/b] Added sound effects to Main Menu and certain in-game events (such as the air dash), increased volume of water rising audio. [*] [b]Controls:[/b] Can now end match and quit game with keyboard controls. [*] [b]Bug Fix:[/b] Removed a situation in which a player's own projectiles could cause damage. [/list] A big thanks to Vaelsh for giving us the feedback about the air dash being controlled by a controller's bumper buttons. We agree... it [b]is[/b] a better place for them.