Update the todo

TODO.markdown

@@ -4,17 +4,12 @@ Must of the stuff is working, but there is a list of smaller
 things that need to be fixed.
 
 * Parsing
-    * $ORIGIN and $INCLUDE 
-    * HIP RR (needs list of domain names, need slice for that);
-* Need to define a handy zone data structure (r/b tree)?.
+    * $INCLUDE 
+* Add handy zone data structure (r/b tree)?
 
 * Use the Exchange structure to deal with errors when resolving, esp. Timeout
 * encoding NSEC3/NSEC bitmaps, DEcoding works;
 * IsSubdomain, IsGlue helper functions;
-* Cleanup?
-* String compression *inside* the library, so the string
-  miek.nl is stored once and all RRs reference it. Would be
-  a major memory saver;
 
 ## Issues