email addresses can only be registered once,
closes #36
adding hint regarding public comments #35
first draft help pages,
sudo pip install django-taggit
add 'taggit' and 'help_pages' to settings/installed apps
help_pages multiple updates,
i18n,
404 template,
style changes
integration of help pages into BuLiTippApp templates
umlaut fix for send_reminders