Allow hspec-wai 0.11 (#1343)

Builds fine and all tests pass.

Author: felixonmars

servant-server/servant-server.cabal

@@ -161,7 +161,7 @@ test-suite spec
       aeson                >= 1.4.1.0  && < 1.6
     , directory            >= 1.3.0.0  && < 1.4
     , hspec                >= 2.6.0    && < 2.8
-    , hspec-wai            >= 0.10.1   && < 0.11
+    , hspec-wai            >= 0.10.1   && < 0.12
     , QuickCheck           >= 2.12.6.1 && < 2.14
     , should-not-typecheck >= 2.1.0    && < 2.2
     , temporary            >= 1.3      && < 1.4