working on Physics system
refactoring into World class
handle collision events (mostly for falling to grounded transitions
added player controls
fixed addEntity (nasty fix, need more overriden methods)
checkCollision now returns collision type
modified nextState to allow for acceleration
added PlayerEntity class
included delta for acceleration
added delta for acceleration
support for PlayerEntity
made data protected, added delta scaling for jump height
added (buggy) run acceleration
random boxes for testing
check bottom collision to initiate falling from grounded state
Merge branch 'master' into collision_refactor