Add brew tap-readme <name> external command.

Closes Homebrew/homebrew#17935.

Library/Contributions/cmd/brew-tap-readme.rb

@@ -0,0 +1,32 @@
+name = ARGV.first
+
+raise "A name is required" if name.nil?
+
+template = <<-EOS
+Homebrew-#{name}
+=========#{'=' * name.size}
+
+How do I install these formulae?
+--------------------------------
+Just `brew tap homebrew/#{name}` and then `brew install <formula>`.
+
+If the formula conflicts with one from mxcl/master or another tap, you can `brew install homebrew/#{name}/<formula>`.
+
+You can also install via URL:
+
+```
+brew install https://raw.github.com/Homebrew/homebrew-#{name}/master/<formula>.rb
+```
+
+Docs
+----
+`brew help`, `man brew`, or the Homebrew [wiki][].
+
+[wiki]:http://wiki.github.com/mxcl/homebrew
+EOS
+
+# puts ERB.new(template, nil, '>').result(binding)
+puts template if ARGV.verbose?
+path = Pathname.new('./README.md')
+raise "#{path} already exists" if path.exist?
+path.write template