Require is bad

So, using `require()` to load dynamic content is Bad Idea. The reason is that require will cache anything it loads. So this is great for loading modules, it is really bad for loading things like levels and nodes, which we want out of memory once we're done with that. I've added a new `utils.require` method which loads the lua object via Love instead of require. This means that when we reload levels, we actually unload the huge lua table that we had to load.

If you guys could test this branch and report back on memory size, that would be great.