Update Travis test-matrix to Django versions supporting migrations

.travis.yml

@@ -1,27 +1,19 @@
 language: python
 python:
   - "2.7"
-  - "3.2"
   - "3.3"
   - "3.4"
 env:
-  - DJANGO=1.6
   - DJANGO=1.7
+  - DJANGO=1.8
   - DJANGO=master
 matrix:
   exclude:
-    - python: "3.4"
-      env: DJANGO=1.6
+    - python: "3.3"
+      env: DJANGO=master
 install:
   - pip install tox coveralls
 script:
   - tox -e py${TRAVIS_PYTHON_VERSION//[.]/}-$DJANGO
 after_success:
   - coveralls
-notifications:
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/2bac49a3941a6612db4c
-    on_success: change  # options: [always|never|change] default: always
-    on_failure: always  # options: [always|never|change] default: always
-    on_start: false     # default: false