Since `vow` now distinguish `promise` and `defer` let's return `promise`, does not make any real difference since defer is already rejected though.

Or better yet, let's always return an <a href="https://github.com/ljharb/node-jscs/blob/a83422b1ab52b20df06df230ff99f79919eb8020/lib/cli.js#L97-101">object</a>, tests for that would be nice to have too.