base: Add release date to changelog

a6819a08 · Ben Gamari · Ryan Scott · 90313820 · a6819a08
Commit a6819a08 authored May 07, 2016 by Ben Gamari 🐢 Committed by Ryan Scott Jul 04, 2016
--- a/libraries/base/changelog.md
+++ b/libraries/base/changelog.md
@@ -12,7 +12,7 @@
  * `New modules `Data.Bifoldable` and `Data.Bitraversable` (previously defined
    in the `bifunctors` package) (#10448)

-## 4.9.0.0  *TBA*
+## 4.9.0.0  *May 2016*

  * Bundled with GHC 8.0