Edit docs for formatting

There are some formatting issues on several of the automatically generated [doc pages](http://craftyjs.com/api/).  This patch is for cleaning up formatting and (where I notice them) grammar issues.

The basic idea here is to just skim the docs, and fix anything that jumps out at me.  :)  It'll be ready to land when we've inspected each of the following modules for obvious problems:

- [x] Core
- [x] Game Loop
- [x] Events
- [x] 2D (But not the math stuff)
- [x] Graphics
- [x] Utilities
- [x] Misc
- [x] Stage
- [x] Input
- [x] Animation
- [x] Scenes
- [x] Audio
- [x] Assets
- [x] Debug