Elchin Valiyev

@ruiterr @nedalhy

Please merge this pull request!

`system` and `file` are used in `lib/jsonlint.js` in the node environment at runtime (https://github.com/zaach/jsonlint/blob/master/lib/jsonlint.js#L430 and https://github.com/zaach/jsonlint/blob/master/lib/jsonlint.js#L424). I would leave them in `dependencies`.