[Answered ]-RemovedInDjango19Warning – isn't in an application in INSTALLED_APPS

According to the error message you posted, the problem is not with your own app but with django.contrib.django.contenttypes.models.ContentType – and googling for this exact error message shows you’re not the first having this issue.

Since contenttypes is in your installed apps, the problem comes from contenttype being imported before being “officialy” loaded. So what you need know is to find out where contenttype is imported and which of these imports happens too soon – or just first try to place it first in your settings INSTALLED_APPS as FeroxTL suggest, it might (or not) solve the problem.