Update Env.cs

Author: mythz

src/ServiceStack.Text/Env.cs

@@ -110,7 +110,7 @@ static Env()
 
         public static string VersionString { get; set; }
 
-        public static decimal ServiceStackVersion = 5.8m;
+        public static decimal ServiceStackVersion = 5.9m;
 
         public static bool IsLinux { get; set; }