integer-simple: Add changelog

libraries/integer-simple/changelog.md

+# Changelog for [`integer-simple` package](http://hackage.haskell.org/package/integer-simple)
+
+## 0.1.1.1 *April 2018*
+
+  * Bundled with GHC 8.6.1
+

libraries/integer-simple/integer-simple.cabal

@@ -9,6 +9,7 @@ description:
     This package contains a simple Integer library.
 cabal-version:  >=1.10
 build-type: Simple
+extra-source-files: changelog.md
 
 source-repository head
     type:     git