Update Travis config

.travis.yml

 sudo: false
-cache:
-  directories:
-    - $HOME/.pip-cache/
 language: python
 python:
   - 2.6
@@ -10,11 +7,11 @@ python:
   - 3.3
   - 3.4
   - 3.5
-addons:
-  postgresql: '9.3'
+services:
+  - postgresql
 install:
   - pip install -r test-requirements.txt
-  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install unittest2 --download-cache $HOME/.pip-cache; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install unittest2; fi
   - python setup.py develop
 script: nosetests
 after_success:
@@ -29,10 +26,3 @@ deploy:
   user: crad
   password:
     secure: UWQWui+QhAL1cz6oW/vqjEEp6/EPn1YOlItNJcWHNOO/WMMOlaTVYVUuXp+y+m52B+8PtYZZCTHwKCUKe97Grh291FLxgd0RJCawA40f4v1gmOFYLNKyZFBGfbC69/amxvGCcDvOPtpChHAlTIeokS5EQneVcAhXg2jXct0HTfI=
-notifications:
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/d96fcd17db66e06d833d
-    on_success: always
-    on_failure: always
-    on_start: always