Complete notifications synchronized

Notifications would reappear after completing the task. The reason was
because an AsyncTask would handle the database operation of removing the
old notification, thus calling notifyPast before the reminder had been
cleared. Now everything is handled on a single thread. Classic race
condition.

Fixes #257

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>
Latest translations included, bump version

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>