code: function (each, done) {
      var self = this
        , tasks = [];
      Object.keys(this.extensions).forEach(function (type) {
        Object.keys(self.extensions[type]).forEach(function (id) {
          var plugin = self.extensions[type][id];
          tasks.push(function (next) {
            each(type, id, plugin, next);
          });
        });
      });
      async.parallel(tasks, done);
    }
docs: allExtensions(each, done) -> done(err, [val, ...]) call `each(type, id, plugin, next(err, val))` for each plugin in parallel