useLanguage = function (key) {
        $uses = key;
        $rootScope.$emit('$translateChangeSuccess', {language: key});

        if ($storageFactory) {
          Storage.put($translate.storageKey(), $uses);
        }
        // inform default interpolator
        defaultInterpolator.setLocale($uses);
        // inform all others too!
        angular.forEach(interpolatorHashMap, function (interpolator, id) {
          interpolatorHashMap[id].setLocale($uses);
        });
        $rootScope.$emit('$translateChangeEnd', {language: key});
      }
@name useLanguage
@private

@description
Makes actual use of a language by setting a given language key as used
language and informs registered interpolators to also use the given
key as locale.

@param {key} Locale key.