Django 1.8 warning: Replace remaining use of django.db.models.loading

[antoviaque]

Use importlib instead of django.db.models.loading - fix remaining occurrences missed by #97

[antoviaque]

@jonashagstedt Do you need any help with the PR review/tests? Happy to help if I can, I would love getting rid of using my fork on my requirements to avoid Django 1.8 warnings - it has been released a while ago now. Thanks!

[hagsteel]

I would love some help.
Other than a full backlog I am battling with the decision wether I'm going to remove the SelfPublishModel (put it in it's own module maybe).

If you want to become more involved in this project let me know and we can have a conversation about it.

[antoviaque]

@jonashagstedt Thanks for the merge! I was more referring to the current review/ticket, to help moving it along - I don't know enough of the project just yet to get more involved, but I've liked what I've seen so far. I'll see if I have other occasions for contribution in the future, and maybe that can lead to more involvement. : )