Merge pull request #1338 from power-fungus/stack-version-requirement

lift required stack-version to 2.1.1

Author: samuelpilz

install/src/Stack.hs

@@ -86,7 +86,7 @@ stackExeIsOldFailMsg stackVersion =
     ++ "Please run `stack upgrade` to upgrade your stack installation"
 
 requiredStackVersion :: RequiredVersion
-requiredStackVersion = [1, 9, 3]
+requiredStackVersion = [2, 1, 1]
 
 -- |Stack build fails message
 stackBuildFailMsg :: String