Update changelog.md

Author: rvl

changelog.md

@@ -1,3 +1,29 @@
+## May 29, 2019
+  * Added `shellFor` function to package set.
+
+## May 28, 2019
+  * Added `snaphots` and `haskellPackages` attributes to the
+    Haskell.nix top-level.
+
+## May 22, 2019
+  * Add the `cleanSourceHaskell` utility function to the Haskell.nix
+    top-level.
+  
+## May 21, 2019
+  * Add the `callCabalProjectToNix` function, which uses "import from
+    derivation" (IFD) so that nix-tools doesn't need to be run
+    manually.
+  * The `hackage.nix` update process has changed, so that Cabal index
+    state hashes are also included in the generated repo.
+
+## May 20, 2019
+  * Remove Travis CI in favour of Buildkite.
+
+## May 17, 2019
+  * Add the `callStackToNix` function, which uses "import from
+    derivation" (IFD) so that `stack-to-nix` doesn't need to be run
+    manually.
+  
 ## Mar 15, 2019
-  * overlays was renamed to extras (#79)  
+  * overlays was renamed to extras (#79)
     See docs/migration.md