no-post-processing

This branch removes the post-processing shaders we were using and adjusts the lighting and fog to look better without the shaders. The lighting and shaders needed an update anyway, but the reason I didn't go that route was the absence of antialiasing. The WebGL renderer has built-in antialiasing that looks pretty good, but when we use post-processing, we lose that antialiasing and have to use some alternative. I plugged in the threejs FXAA shader, which looked good up close, got really blurry in the distance, and didn't seem to remove the aliasing in between.

My monitor at home isn't very nice, so the aliasing issue is extremely noticeable. I think it is more important to have good antialiasing than the shaders we currently have. I'd like to explore our options to get decent antialiasing and post-processing, because I think some post-processing effects could add a lot to the visual feel of the game. For instance, adding some glare or glow around bright spots on objects or depth of field. That may need to wait until after June, though. 

If you have any suggestions on the lighting or anything in this branch, let me know.

Anyway, what do you guys think about dropping the post-processing in favor of anti-aliasing?

@kadst43 @eric79 @scottnc27603