Make the app thread safe

[soynatan]

From u/boxidea in r/django:

I don't think that storing the request on the EasyAuditMiddleware class is a good idea.

Middleware classes are shared across requests, so anything you store on the class is not going to be thread safe.

https://www.reddit.com/r/django/comments/5ux246/hello_everyone_i_created_a_simple_django_app_to/ddxpw8n/

[jheld]

@soynatan any update on this?

[soynatan]

No, I haven't had any time to check this. I opened the issue so I wouldn't forget about it. If you want to try this fix go ahead, otherwise I'll do it in a couple of days.

[soynatan]

I applied the fix. Seems to be working ok. We'll open another issue if it causes any problem.