Alpha 004a - Zombie Update

Changes:

+Added the ability to walk up single blocks and pixels like stairs (a bit buggy though)
+Added zombie aggroing when the player is within 8 blocks or when player attacks
*Changed loading screen when generating a world
*Changed pause menu to actually be a pause menu, not a quit button


Bug fixes:

Fixed character animation resetting to walking after jumping and falling even when pressing sprint
Fixed zombies not despawning outside of the player's view
(Partly) fixed zombies spawning inside of blocks occasionally
Fixed lag when going to the main menu (caused by downloading the latest version number each time you visit the menu)