Add brew-profile to contrib

This command loads all formulae and dumps an HTML profile report to
stdout. So e.g. `brew profile >/tmp/report.html`

Library/Contributions/cmd/brew-profile.rb

@@ -0,0 +1,12 @@
+begin
+  require 'rubygems'
+  require 'ruby-prof'
+rescue LoadError
+  abort 'This command requires the ruby-prof gem'
+end
+
+require 'formula'
+
+RubyProf.start
+Formula.names.each { |n| Formula.factory(n) }
+RubyProf::GraphHtmlPrinter.new(RubyProf.stop).print(STDOUT)