travis: removed testing on nightly, exclude testing django 1.9 on pyt…

…hon 3.3, upgrade django versions to test on.

.travis.yml

@@ -7,23 +7,22 @@ python:
 - 3.5
 - pypy
 - pypy3
-- nightly
 
 env:
-- DJANGO_VERSION=1.7.10
-- DJANGO_VERSION=1.8.4
-- DJANGO_VERSION=1.9b1
+- DJANGO_VERSION=1.7.11
+- DJANGO_VERSION=1.8.7
+- DJANGO_VERSION=1.9
 
 matrix:
   allow_failures:
     - python: pypy
     - python: pypy3
-    - python: nightly
-    - env: DJANGO_VERSION=1.9b1
   exclude:
     # Django 1.7 is not supported on python 3.5.
     - python: 3.5
       env: DJANGO_VERSION=1.7.10
+    - python: 3.3
+      env: DJANGO_VERSION=1.9
 
 install:
 - pip install -q -r requirements.txt