Allow containers-0.7

req.cabal

@@ -39,7 +39,7 @@ library
         blaze-builder >=0.3 && <0.5,
         bytestring >=0.10.8 && <0.13,
         case-insensitive >=0.2 && <1.3,
-        containers >=0.5 && <0.7,
+        containers >=0.5 && <0.8,
         crypton-connection >=0.3 && <0.5,
         data-default-class,
         exceptions >=0.6 && <0.11,