update README

README.md

-* Jose's comparator tests
 * Balloon stuff -- a bit complicated, but useful to show constructor references
 * Maurice's forEach example List<StringBuilder>
-* reorganize files
+* reorganize files:
+   C - default methods
+   D - simple streams and collectors
+   E - composite collectors
+   F - custom collectors
+   G - challenges
+   
 
 Java 8 Lambdas Hands-on Lab Materials