Update changelog.

Author: bodil

CHANGELOG.md

@@ -7,18 +7,19 @@ adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
-#189 #197
-
-#163 #150 #154 #191 #186 #179 #173 #194 #158 
-
 ### Added
 
 -   `HashSet` now implements `From<Vector<A>>` and `From<&Vector<A>> where A: Clone`.
 
 ### Fixed
 
+-   Fixed a long standing crash bug in `OrdMap`/`OrdSet`. (#154, #143, #152, #124)
+-   The `union` method on maps/sets will now prefer to mutate the larger set (which leads to less
+    work) rather than the first set. (#163)
+-   Ensure `TreeFocus` only implements `Send`/`Sync` when the underlying type does. (#157, #158)
 -   There was an issue where nodes in very large `OrdMap`s could overflow when removing an element
     and cause a panic, which has now been fixed. (#141)
+-   Assorted doc cleanup. (#150, #173, #186, #194)
 
 ## [15.0.0] - 2020-05-15