E-Mail notifications

Had added a feature request in issues: http://projectpier.org/node/643
Would be nice to have email notifications for task overdue, if a calender is intergrated, then notification of pending meeting, etc.

It is good to notify a user when a milestone has been assigned to them, but I believe it is essential to be able to send a notification when that milestone is due/over due and has not been completed.

Mark C.