Feature request: add `from!` function returning just the path of the downloaded file

[ls6]

Thanks for writing this module. I was considering writing such mechanism myself but I was delighted to find out I don't need to shave that yak :)

Currently I have file download as a fist stage in a pipe, passing the downloaded file path to the next stage. I suspect it could be a common pattern much like HTTPoison.request/5 vs HTTPoison.request!/5, so it may be worth adding to your module.

I would happily supply a PR but I'm about to leave for computer-free holidays :)

[asiniy]

@ls6 enjoy your holiday! Feel free to supply PR after your vacation