Homebrew/homebrew — pull request #34569 by weakish (2014-11-30 16:49:46+00:00)
Title: doc/External-Commands: update links.

`brew-gem`'s link is 404.
`brew-pip` has reached EOL.
Thus I updates the link of `brew-gem`, and remove descriptions
about `brew-pip`.

Thanks @DomT4 for pointing out brew-gem's new home.

close 34563