* General
   * Local comments becomes disabled by default.
     Now you have to specify `--enable-local-comment` option to activate the UI and endpoint.
   * Schema is changed.
     * Now actor's metadata is stored into another `Actors` table.
     * New column `tags` is introduced and `scope` is migrated to a tag.
     * Migration script `migrate-0.3.0-to-0.4.0` is now available.
   * The navigation bar is fixed on the top.
   * A menu button is available in the navigation bar for narrow screens.
   * Timestamp filters can be applied more easily.
     You don't have to calculate UNIX time manually anymore.
   * Datetime picker is now available to set target range filters.
   * Errors around null response from the Groonga server are suppressed.
 * Archive view
   * Becomes exportable as CSV and JSON.