Remove hgreview from how to develop
I think we should remove reference to hgreview. Last version is broken on recent mercurial. I think @nicoe is not going to maintain and even more the next release of mercurial will start supporing Python3.
I have created a PR to improve the workflow of upload.py [1] and wrote a small script to mimic the hgreview features [2] as example.
[1] https://github.com/rietveld-codereview/rietveld/pull/572
[2] https://pastebin.com/EjNyhGjD