added help text for genetor function

Author: sgaurav

generators.js

@@ -1,3 +1,8 @@
+/**
+  * Generators are functions which can be paused and resumed later. Function 
+  * context is saved across resumes.
+  */
+
 function* count(){
   var start = 0;
   while(true) {
@@ -11,4 +16,4 @@ var iterator = count();
 iterator.next(); //{value: 0, done: false}
 iterator.next(); //{value: 1, done: false}
 iterator.next(); //{value: 2, done: false}
-iterator.next(); //{value: 3, done: false}
+iterator.return();