Fix lower bound on containers

Author: sjakobi

unordered-containers.cabal

@@ -94,7 +94,7 @@ test-suite unordered-containers-tests
   build-depends:
     base,
     ChasingBottoms,
-    containers >= 0.4.2,
+    containers >= 0.5.8,
     hashable >= 1.0.1.1,
     HUnit,
     QuickCheck >= 2.4.0.1,