CHANGELOG: update to include vtables & kobject_copy()

CHANGELOG.md

@@ -79,6 +79,11 @@ changes, deprecations, removals, and fixes.
   supported.  See examples/median.py for a simple median filter
   implementation using KazePy!
 
+- KObjects now have virtual function tables.  This expands upon
+  destructors to now include copy constructors.  With this addition also
+  comes `kobject_copy()`, which produces deep copies of KObjects using
+  the provided KObject's virtual copy constructor method.
+
 ### Changed
 - Make `KObject` the primary data object type.  `KObject` is now used to
   support both Kaze Images and Histograms.  This means that functions