Require servant-0.18.2 in servant-swagger

This version of servant adds Fragment, which servant-swagger adds
instance for.

Author: maksbotan

servant-swagger/servant-swagger.cabal

@@ -77,7 +77,7 @@ library
                      , http-media                >=0.7.1.3  && <0.9
                      , insert-ordered-containers >=0.2.1.0  && <0.3
                      , lens                      >=4.17     && <6
-                     , servant                   >=0.18.1   && <0.20
+                     , servant                   >=0.18.2   && <0.20
                      , singleton-bool            >=0.1.4    && <0.2
                      , swagger2                  >=2.3.0.1  && <3
                      , text                      >=1.2.3.0  && <2.1