implement pluralization for server-side and js

app/assets/javascripts/locales/cs.js.erb

@@ -1,3 +1,10 @@
 //= depend_on 'client.cs.yml'
 //= require locales/i18n
 <%= JsLocaleHelper.output_locale(:cs) %>
+
+I18n.pluralizationRules['cs'] = function (n) {
+  if (n == 0) return ["zero", "none", "other"];
+  if (n == 1) return "one";
+  if (n >= 2 && n <= 4) return "few";
+  return "other";
+}