Update CHANGELOG

CHANGELOG

@@ -1,6 +1,9 @@
 master (Release Candidate for v0.2.0)
 
 * Begin FederateAPI unofficial implementation report.
+* All 'vocab.Object' types and types extending from 'vocab.Object' now have an
+      'IsPublic' method that will return true if the 'to', 'bto', 'cc', or 'bcc'
+      properties have the ActivityPub special Public collection IRI.
 * Use 'OrderedCollection' as the default type for 'likes', 'liked',
       'following', and 'followers' properties if the actor or object does not
       have an IRI, 'Collection', or 'OrderedCollection' set for these