Send emails when password or email address are change for user

I am adding the functionality requested in #378 to send out emails to the user when their email address or password are changed.

The sending of emails is handled in the ``ChangePasswordView`` and ``ProfileUpdateView`` respectively. I am not sure if this is the right way to do it, especially for the email address update. I feel like there should be a better solution to looking up the current data from the database in the view and comparing it to the form. Any suggestions? 

Let me know if I need to change anything for this to get merged.