Bump upper bound on base to < 4.13

RyanGlScott · web-flow · commit 4e42eb37222a · 2018-04-10T07:36:45.000-04:00
See https://ghc.haskell.org/trac/ghc/ticket/15018.
diff --git a/filepath.cabal b/filepath.cabal
@@ -48,7 +48,7 @@ library
         System.FilePath.Windows
 
     build-depends:
-        base >= 4 && < 4.12
+        base >= 4 && < 4.13
 
     ghc-options: -Wall
 
