Made get_occurrence work for one-time events
Made get_occurrence work for one-time events

Signed-off-by: thauber <ec9c61b22d79ca9ae8f3366175a92e4f50a852c4@gmail.com>
llazzaro/django-scheduler,GrahamDigital/django-scheduler,jrutila/django-schedule,jrutila/django-schedule,nharsch/django-scheduler,ixc/glamkit-eventtools,sprightco/django-scheduler,nharsch/django-scheduler,nwaxiomatic/django-scheduler,drodger/django-scheduler,nwaxiomatic/django-scheduler,mbrondani/django-scheduler,nwaxiomatic/django-scheduler,Gustavosdo/django-scheduler,erezlife/django-scheduler,jrutila/django-scheduler,rowbot-dev/django-scheduler,drodger/django-scheduler,GrahamDigital/django-scheduler,sprightco/django-scheduler,sprightco/django-scheduler,Gustavosdo/django-scheduler,jrutila/django-schedule,erezlife/django-scheduler,rowbot-dev/django-scheduler,jrutila/django-scheduler,drodger/django-scheduler,llazzaro/django-scheduler,llazzaro/django-scheduler,GrahamDigital/django-scheduler,ixc/glamkit-eventtools,mbrondani/django-scheduler