Add Django 1.9 to test matrix

Signed-off-by: Michal Čihař <michal@cihar.com>

.travis.yml

@@ -20,11 +20,16 @@ env:
     - CI_PIP_DEPS="Django>=1.8,<1.9" CI_DATABASE=postgresql
     - CI_PIP_DEPS="Django>=1.7,<1.8"
     - CI_PIP_DEPS="Django>=1.8,<1.9"
+    - CI_PIP_DEPS="--pre django"
     - CI_PIP_DEPS="Django>=1.8,<1.9" CI_DATABASE=postgresql CI_MODE=selenium
   global:
     - DJANGO_SETTINGS_MODULE=weblate.settings_test
     - CI_REQUIREMENTS=travis
     - CI_MODE=test
+matrix:
+  allow_failures:
+    - python: "2.7"
+      env: CI_PIP_DEPS="--pre django"
 # commands to install dependencies
 install:
   - ./ci/install