unzip: implement without directly delegating to lodash

[dflemstr]

For the sake of iteration speed, a lot of rq functionality was implemented by directly delegating to lodash. This is not optimal because the use of this.collect() and/or this.spread() means that intermediary arrays are allocated unnecessarily. The code of unzip should be changed to abuse the streaming nature of rq processes while still passing the current doctests. For debugging, tee can be used to check the streaming behavior of the process.