docker, boot2docker: note about updates.

docker and boot2docker generally release new versions simultaneously.
This is because boot2docker's ISO contains docker within it.

This comment just reminds people who update one to update the other.

Closes Homebrew/homebrew#31110.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Formula/boot2docker.rb

@@ -2,6 +2,8 @@ require "formula"
 
 class Boot2docker < Formula
   homepage "https://github.com/boot2docker/boot2docker-cli"
+  # Boot2docker and docker are generally updated at the same time.
+  # Please update the version of docker too
   url "https://github.com/boot2docker/boot2docker-cli.git", :tag => "v1.1.1"
   head "https://github.com/boot2docker/boot2docker-cli.git", :branch => "master"
 

Formula/docker.rb

@@ -2,6 +2,8 @@ require "formula"
 
 class Docker < Formula
   homepage "http://docker.io"
+  # Boot2docker and docker are generally updated at the same time.
+  # Please update the version of boot2docker too
   url "https://github.com/dotcloud/docker.git", :tag => "v1.1.2"
 
   bottle do