adding somewhat sketchy assumption for HQ_NOTIFICATIONS_EMAIL for dimagi-utls, defaults to standard django assuptions, EMAIL_HOST_USER, vs. old hq assumptions, EMAIL_LOGIN
cleanup and adding email_from kwarg to allow override of from field in cases where the in built django assumptions are not valid email addresses (amazon SES)
Merge pull request #87 from dimagi/email_notifications

adding somewhat sketchy assumption for HQ_NOTIFICATIONS_EMAIL for dimagi...