code: function hmu (requests, callback) {
    if (!callback) callback = _noop
    pull(stream(requests), collect(callback))
  }
docs: Run HMU requests and get raw output.
  `requests` being an array of objects.
  { target: fn, input: [], options: {} }
  `callback` being a function with params (err, res)
  `res` being an array of arrays, in order of the requests.
  Normally they are just some mapping/reduce of `input`