#354 Add maven model for feature toggle design pattern

callback/index.md

@@ -11,16 +11,18 @@ tags:
  - Idiom
 ---
 
-**Intent:** Callback is a piece of executable code that is passed as an
+## Intent
+Callback is a piece of executable code that is passed as an
 argument to other code, which is expected to call back (execute) the argument
 at some convenient time.
 
 ![alt text](./etc/callback.png "Callback")
 
-**Applicability:** Use the Callback pattern when
+## Applicability
+Use the Callback pattern when
 
 * when some arbitrary synchronous or asynchronous action must be performed after execution of some defined activity.
 
-**Real world examples:**
+## Real world examples
 
 * [CyclicBarrier] (http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept callback that will be triggered every time when barrier is tripped.