Move tutorial individual page to /resources/tutorials/ (#503)

Author: renatoalencar

pages/[lang]/resources/[tutorial].res renamed to pages/[lang]/resources/tutorials/[tutorial].res

@@ -65,7 +65,7 @@ let toString = (t: t, lang) => {
   | #ResourcesReleases => "resources/releases"
   | #ResourcesUsingocaml => "resources/usingocaml"
   | #ResourcesTutorials => "resources/tutorials"
-  | #ResourcesTutorial(s) => "resources/" ++ s
+  | #ResourcesTutorial(s) => "resources/tutorials/" ++ s
   }
   "/" ++ lang ++ "/" ++ path
 }