Proposal: support new request to writer

[gonejack]

It will be more easy to migrate from code like io.Copy(writer, resp.Body) to grab if grab supports new download to an opened writer.

grab.NewRequestToWriter(writer io.Writer, url string)

[cellargalaxy]

yes, it is a good feature, i would also like to support this feature

[opensaucerer]

@gonejack @cellargalaxy check this out. I just added support for grab.NewRequestToWriter.
https://github.com/opensaucerer/grab#this-extended-version-of-the-original-cavaliergophergrab-now-allows-you-to-download-files-into-a-given-iowriter