Add explicit test against Django 1.11+

Author: andrlik

tox.ini

@@ -6,9 +6,9 @@ exclude = docs/*
 
 [tox]
 envlist =
-    py27-django{18,19,10},
-    py34-django{18,19,10,_trunk},
-    py35-django{18,19,10,_trunk}
+    py27-django{18,19,10,11},
+    py34-django{18,19,10,11,_trunk},
+    py35-django{18,19,10,11,_trunk}
 
 [testenv]
 basepython = 
@@ -23,6 +23,7 @@ deps =
     django18: Django>=1.8,<1.9
     django19: Django>=1.9,<1.10
     django10: Django>==10
+    django11: Django>=1.11,<1.12
     django_trunk: https://github.com/django/django/tarball/master
 
 commands =