Merge pull request #34 from gadilashashank/master

Add JS entry

Author: gadilashashank

book/SUMMARY.md

@@ -55,6 +55,20 @@
 
   * [Conclusion](languages/python/conclusion.md)
 
+* [JavaScript](languages/js/README.md)
+
+  * [Introduction](languages/js/intro.md)
+
+  * [History](languages/js/history.md)
+
+  * [Purpose & Advantages](languages/js/advantages.md)
+
+  * [Disadvantages](languages/js/disadvantages.md)
+
+  * [Some interesting facts](languages/js/misc.md)
+
+  * [Conclusion](languages/js/conclusion.md)
+
 * [C#](languages/csharp/README.md)
 
   * [Introduction](languages/csharp/intro.md)