update changelog for 2.3.0

CHANGELOG.md

@@ -1,3 +1,7 @@
+# v2.3.0
+- Added support for ES2017 `async` functions.  Wherever you can pass a Node-style/CPS function that uses a callback, you can also pass an `async` function.  Previously, you had to wrap `async` functions with `asyncify`.  The caveat is that it will onyl work if `async` functions are supported nateively in your environment, transpilied implementations can't be detected.  (#1386, #1390)
+- Small doc fix (#1392)
+
 # v2.2.0
 - Added `groupBy`, and the `Series`/`Limit` equivalents, analogous to [`_.groupBy`](http://lodash.com/docs#groupBy) (#1364)
 - Fixed `transform` bug when `callback` was not passed (#1381)