0.5.3 release
* Bugfix: Cascade top document's level to subframes with no explicitly assigned level. (workaround
for Github issue #133).
* Bugfix: Improve IPv6 handling in NBS
* Bugfix (Chromium-based browsers): Fix per-domain level options/settings page (Github issue #147)
* Do not display NBS notifactions when accessing 0.0.0.0 and :: (workaround
for Github issue #125)
* Improve NBS description in the option/settings page.
* Display level names in the pop up to improve usability.