adding marble diagram to combineLatest() javadoc

Adding a marble diagram that describes combineLatest() to the javadoc
section for that method

Author: DavidMGross

rxjava-core/src/main/java/rx/Observable.java

@@ -2806,6 +2806,9 @@ public static <R> Observable<R> zip(Collection<Observable<?>> ws, final Object f
     /**
      * Combines the given observables, emitting an event containing an aggregation of the latest values of each of the source observables
      * each time an event is received from one of the source observables, where the aggregation is defined by the given function.
+     * <p>
+     * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-operators/combineLatest.png">
+     * 
      * @param w0 
      *          The first source observable.
      * @param w1