New exception notifier

On a quest of getting rid of Rails 2.3 style plugin warnings removed the
old exception_notifier from vendor and replaced it with
exception_notification, a gem still being maintained.
Removed also dynamic-form

dynamic_form is found from rubygems and seems to be working as expected,
so removed the whole vendor folder and included it as a gem.
Updated rspec to get rid of warnings

Old rspec caused deprecation warnings. New one does not.
Merge branch 'dev'