caveats: print .app caveats if installed to keg.

Library/Homebrew/caveats.rb

@@ -13,6 +13,7 @@ class Caveats
     caveats << zsh_completion_caveats
     caveats << plist_caveats
     caveats << python_caveats
+    caveats << app_caveats
     caveats.compact.join("\n")
   end
 
@@ -59,6 +60,15 @@ class Caveats
     end
   end
 
+  def app_caveats
+    if keg and keg.app_installed?
+      <<-EOS.undent
+        .app bundles were installed to #{f.prefix} (or libexec).
+        Run `brew linkapps` to symlink these to /Applications.
+      EOS
+    end
+  end
+
   def plist_caveats
     s = []
     if f.plist or (keg and keg.plist_installed?)