added notification email for the responsible user (accept/decline). #69
Merge branch 'develop-ak' of https://github.com/tkowark/hpi-hiwi-portal into develop-ak

:q!
merge
added student notifications for applications accepted/declined #67
added ApplicationMailer file to the git
added job offer student accpeted & offer closed notifs for HPI staff #120
Merge remote-tracking branch 'origin/develop-ak' into develop