Update django-model-utils from 2.6 to 3.0.0

Author: pyup-bot

project/requirements/base.txt

@@ -15,7 +15,7 @@ django-crispy-forms==1.6.1
 django-floppyforms==1.7.0
 
 # Models
-django-model-utils==2.6
+django-model-utils==3.0.0
 
 # Images
 Pillow==3.4.2