Update changelog

Author: dhardy

CHANGELOG.md

@@ -11,7 +11,8 @@ You may also find the [Upgrade Guide](https://rust-random.github.io/book/update.
 
 ## [0.6.4] - 2019-01-08
 ### Fixes
-- Move wasm-bindgen shims to correct crate (#682)
+- Move wasm-bindgen shims to correct crate (#686)
+- Make `wasm32-unknown-unknown` compile but fail at run-time if missing bindingsg (#686)
 
 ## [0.6.3] - 2019-01-04
 ### Fixes