code: function fetchAuthors (forPackages, opts) {
    opts = normalizeOpts(opts)
    // start with npmUser and email from registry
    return fetchRegistry(forPackages, {}, opts)
      .then(persons => {
        // reduce duplicates and add pre-known aliases
        return reduceDuplicates(persons, opts)
      })
      .then(persons => {
        // add name, githubUser, and twitter from npm profile
        return fetchProfiles(persons, opts)
      })
      .then(persons => {
        // finish with name and email from github
        return fetchGithub(persons, opts)
      })
  }
docs: returns a Promise that resolves to fetched authors