Lint all the JSON!

- Add a `jsonlint` Grunt target.
- Add 'jsonlint' to the 'lint' target.
- Reorder the package.json file dependencies and devDependencies.
- Add missing copyright header which was failing the main `grunt` task.

```
$ grunt lint copyright
Running "jshint:grunt" (jshint) task

✔ No problems


Running "jshint:app" (jshint) task

✔ No problems


Running "jshint:tests" (jshint) task

✔ No problems


Running "jsonlint:config" (jsonlint) task
>> 2 files lint free.

Running "jsonlint:app" (jsonlint) task
>> 25 files lint free.

Running "jscs:src" (jscs) task
>> 119 files without code style errors.

Running "copyright:app" (copyright) task

Done, without errors.
```