Remove the master branch plz

[l29ah]

https://matthew-brett.github.io/pydagogue/gh_delete_master.html

[conorsch]

Doesn't seem like a good idea to me. I'd say there's an argument for updating the default branch on the repo not to be master, but that's as far as I'd go. Personally the way the repo works at present is quite intuitive to me.

[l29ah]

What's the point of keeping the old upstream master branch around?