Fixed typos and added a screenshot

Author: Raven G. Duran

avl.c

@@ -2,10 +2,10 @@
 // Feel free to use the source code for any of your project and don't forget to share! :)
 
 
-// Kung feeling nimo naka tabang ko... Ok ra sa ako libre burger. haha xD
+// Kung feel nimo mang libre, OK ra sa ako. haha xD
 
 #include <stdio.h>
-#include <math.h>
+#include <math.h> // for the abs() function. (Absolute value)
 
 
 struct node {

documentation.md

@@ -1,5 +1,9 @@
+Screenshots
+===========
+![AVL Tree](http://i.imgur.com/wTLbV.png "Program Frame Screenshots")
+
 Documentation
-========
+=============
 
 This is the documentation for the source code. I'll update it from time to time if I found bugs or things that
 need to be discussed.