Update documentation links.

CONTRIBUTING.md

Library/Homebrew/README.md

Library/Homebrew/cask/README.md

Library/Homebrew/cmd/help.rb

Library/Homebrew/cmd/info.rb

Library/Homebrew/cmd/tap-info.rb

Library/Homebrew/dev-cmd/create.rb

Library/Homebrew/dev-cmd/tap-readme.rb

Library/Homebrew/formula.rb

Library/Homebrew/manpages/brew.1.md.erb

Library/Homebrew/utils/analytics.rb

Library/Homebrew/utils/analytics.sh

README.md

docs/Common-Issues.md

docs/External-Commands.md

docs/Formula-Cookbook.md

docs/New-Maintainer-Checklist.md

docs/Node-for-Formula-Authors.md

docs/Prose-Style-Guidelines.md

docs/Tips-N'-Tricks.md