Use django-modelcluster 4.0

setup.py

@@ -22,9 +22,9 @@ except ImportError:
 
 install_requires = [
     "Django>=1.11,<2.1",
-    "django-modelcluster>=3.1,<4.0",
+    "django-modelcluster>=4.0,<5.0",
     "django-taggit>=0.20,<1.0",
-    "django-treebeard>=3.0,<5.0",
+    "django-treebeard>=4.2.0,<5.0",
     "djangorestframework>=3.1.3,<4.0",
     "Pillow>=2.6.1,<5.0",
     "beautifulsoup4>=4.5.1,<5.0",

tox.ini

@@ -43,7 +43,6 @@ deps =
     dj111-mssql: django-pyodbc-azure==1.11.0.0
     dj20: Django>=2.0,<2.1
     dj20: git+https://github.com/jdufresne/django-taggit.git@dj20
-    dj20: git+https://github.com/wagtail/django-modelcluster.git
     postgres: psycopg2>=2.6
     mysql: mysqlclient==1.3.6
     elasticsearch2: elasticsearch>=2,<3