usage.rd in rabbit-2.1.3

- old
+ new

@@ -16,5 +16,9 @@
   * ((<"rabbiter/"/Rabbiter>)): It's a tool that receives comments
     from Twitter and passes them to Rabbit. Rabbit displays received
     comments on the current slide.
   * ((<"rabwii/"/RabWii>)): A Wii Remote interface for Rabbit. You can
     control Rabbit by your Wii Remote.
+
+Here are platform specific usages:
+
+  * ((<"usage/platform/os-x.rd"/OS X specific Rabbit usage>))