Smarter export statements

To try out:

- Somewhere outside EAK: `git clone
  git@github.com:thomasboyt/es6-module-transpiler.git`
- In the cloned repo: `npm link`
- In EAK: `cd node_modules/grunt-es6-module-transpiler`
- `npm link es6-module-transpiler`
Support __default__ on loader