Update do Django 2.0

[cuducos]

What is the problem?
Django 2.0 has some incompatibilities with Django 1.11.7 (actual version) and maybe our dependencies also might be broken with we update to 2.0.

How can this be addressed?

• Wait for django-simple-history to be ready for Django 2.0 (tks @giovanisleite)
• Wait for mixer to be ready for Django 2.0
• Update syntax for urls.py

What else? Please, comment on the topic and I can edit this post to complete this list.

Who could help with this issue?
@anaschwendler @giovanisleite