Notice delete task

A specific rake task to delete Notices that are 3 days old. Maybe this should take a parameter, but we've found that 3 days works well for us.

We found that we have over 5000 Notices which filled up our Monogo DB. This should keep it well under that limit.

**This will delete all information under your problem (backtrace, server environment, etc.).**

You can add this into heroku's scheduler: rake errbit:db:delete_notices