Split owner and repo names into separate parameters

- `ghlint.lintRepo(repo, callback)` is now
  `ghlint.lintRepo(owner, repo, callback)`.
- `ghlint.lintUserRepos(repo, callback)` is now
  `ghlint.lintReposByOwner(owner, callback)`.
- RepoResults now have separate `owner` and `name` properties.
- The CLI's usage has not changed.