Har mergeat ihop level och gameplaystate till en fil som heter
Level1 för att lättare kunna skapa nya levels.
Can now switch between level 1 and 2 by pressing 1 or 2 on the
keyboard. Level1.js and Level2.js are the level files.
Added a level superclass Level.js. When inheriting from that class you
create a level by defining the function loadLevelObjects in the
subclass.
Changed so that the size of the world is defined in the Level.js
constructor.
Added an addPlatform function to Level.js.
Merge pull request #14 from samni698/levels

Levels