deps: move recursive_deps_tree into Homebrew module

Library/Homebrew/cmd/deps.rb

 require 'formula'
 
-def recursive_deps_tree f, level
-  f.deps.default.each do |dep|
-    puts "|  "*(level-1)+"|- "+dep.to_s
-    recursive_deps_tree(Formula.factory(dep), level+1)
-  end
-end
-
 module Homebrew extend self
   def deps
     if ARGV.include? '--installed'
@@ -33,6 +26,13 @@ module Homebrew extend self
       puts all_deps
     end
   end
+
+  def recursive_deps_tree f, level
+    f.deps.default.each do |dep|
+      puts "|  "*(level-1)+"|- "+dep.to_s
+      recursive_deps_tree(Formula.factory(dep), level+1)
+    end
+  end
 end
 
 class Array