remove assistive_devices caveat in arranger

Casks/arranger.rb

@@ -9,5 +9,14 @@ cask :v1 => 'arranger' do
   license :unknown
 
   app 'Arranger.app'
-  caveats 'Note that Arranger also needs access for assistive devices (Accessibility)'
+
+  # todo: replace with new assistive_devices stanza
+  caveats do
+    <<-EOS.undent
+      To use #{@cask}, you may need to give it access to assistive
+      devices (Accessibility).  For OS X Mavericks and Above:
+
+        System Preferences / Security & Privacy / Privacy / Accessibility
+    EOS
+  end
 end