Test against Django 1.11 but allow failures (adamchainz#198)

Since tests are currently failing (see adamchainz#197). The `>=1.11a1,<2.0`
specifier will avoid having to adjust the version as the Django 1.11
pre-release cycle continues.

Django 1.11 now requires pytz, so this has to be pinned due to the use
of `--no-deps` in the Tox pip install command.

Author: edmorley

requirements.in

@@ -5,4 +5,5 @@ multilint
 pytest
 pytest-cov
 pytest-django
+pytz
 Pygments

requirements.txt

@@ -19,3 +19,4 @@ Pygments==2.1.3
 pytest-cov==2.4.0
 pytest-django==3.1.2
 pytest==3.0.5
+pytz==2016.10

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 envlist =
     py{27,35}-codestyle,
-    py{27,35}-django{18,19,110}
+    py{27,35}-django{18,19,110,111}
 
 [testenv]
 setenv =
@@ -12,8 +12,17 @@ deps =
     django18: Django>=1.8,<1.9
     django19: Django>=1.9,<1.10
     django110: Django>=1.10,<1.11
+    django111: Django>=1.11a1,<2.0
 commands = ./runtests.py {posargs}
 
+# Tests currently fail under Django 1.11:
+# https://github.com/ottoyiu/django-cors-headers/issues/197
+[testenv:py27-django111]
+ignore_outcome = True
+
+[testenv:py35-django111]
+ignore_outcome = True
+
 [testenv:py27-codestyle]
 commands = multilint