Update to treebeard 3.0. Fixes #930

docs/requirements.txt

@@ -1,5 +1,5 @@
 Django>=1.6.2,<1.8
 django-modelcluster>=0.4
 django-taggit==0.12.2
-django-treebeard==2.0
+django-treebeard==3.0
 six>=1.7.0

setup.py

@@ -33,7 +33,7 @@ install_requires = [
     "django-libsass>=0.2",
     "django-modelcluster>=0.4",
     "django-taggit==0.12.2",
-    "django-treebeard==2.0",
+    "django-treebeard==3.0",
     "Pillow>=2.6.1",
     "beautifulsoup4>=4.3.2",
     "html5lib==0.999",

tox.ini

@@ -5,7 +5,7 @@ base =
     libsass==0.5.1
     django-modelcluster>=0.3
     django-taggit==0.12.1
-    django-treebeard==2.0
+    django-treebeard==3.0
     Pillow>=2.3.0
     beautifulsoup4>=4.3.2
     html5lib==0.999