Modify from "rm" to "rm -f" in go-setup.sh
Modify the command for installation "hk"

Ref. https://github.com/heroku/hk/tree/4e01c29331ad0d1ff3f7e00feddfe782ce7b5734#mac-os-x-linux-bsd

Remove the mercurial installation and the guide of "hk login"