Fix the redirect on submissions#destroy
Fix the redirect on submissions#destroy

It now goes to Manage Submissions, instead of handin history.
Fixes #95

wcyz666/Autolab,AEgan/Autolab,autolab/Autolab,autolab/Autolab,cagdasbas/Autolab,jez/Autolab,cg2v/Autolab,cagdasbas/Autolab,jez/Autolab,wcyz666/Autolab,cg2v/Autolab,kk262777/Autolab,autolab/Autolab,anusornc/Autolab,anusornc/Autolab,anusornc/Autolab,wcyz666/Autolab,wcyz666/Autolab,kk262777/Autolab,cagdasbas/Autolab,AEgan/Autolab,cg2v/Autolab,cg2v/Autolab,AEgan/Autolab,yunfanye/Autolab,yunfanye/Autolab,cagdasbas/Autolab,kk262777/Autolab,cagdasbas/Autolab,yunfanye/Autolab,cagdasbas/Autolab,yunfanye/Autolab,cg2v/Autolab,kk262777/Autolab,autolab/Autolab,autolab/Autolab,AEgan/Autolab,wcyz666/Autolab,anusornc/Autolab,jez/Autolab,kk262777/Autolab,AEgan/Autolab,kk262777/Autolab,autolab/Autolab,jez/Autolab,yunfanye/Autolab,yunfanye/Autolab,AEgan/Autolab,jez/Autolab,cg2v/Autolab,anusornc/Autolab