code style cleanup.

@CWSpear please check this out whenever you have time. I did a little shifting around of code. The main changes:

1. Change `var yo = function () {};` to `function yo() {}`.
2. Use [`modmod`](https://github.com/stephenplusplus/modmod) to change multiple line var decls/requires into a one liner. External dependencies now look like `var $ = require('modmod')('fs', 'path');`, then are namespaced under `$`: `$.fs.readFile();`
3. Moved the default file type object to its own file, `default-file-types.js`.

All the tests pass, and things look happy. Just wanted a second set of :eyes: for a sanity check.
Is there any advantage to this other than not polluting the global namespace?