Bump version to 0.5.3 and update changelog

array.cabal

 name:          array
-version:       0.5.2.0
+version:       0.5.3.0
 -- NOTE: Don't forget to update ./changelog.md
 license:       BSD3
 license-file:  LICENSE

changelog.md

 # Changelog for [`array` package](http://hackage.haskell.org/package/array)
 
-## Next
+## 0.5.3.0  *Oct 2018*
 
-  * Bundled with GHC 8.6.1
+  * Bundled with GHC 8.6.2
   * Drop support for GHC versions prior to GHC 8.0
 
 ## 0.5.2.0  *Jul 2017*