Merge pull request #21 from edx/db/coveralls

Have Travis inform Coveralls of coverage information

.travis.yml

 language: python
 python:
   - "2.7"
-install: "pip install -r requirements.txt --use-mirrors"
-script: python manage.py test notifier
+install:
+  - pip install -r requirements.txt
+  - pip install coveralls
+script:
+  - python manage.py test notifier
+after_success:
+  - coveralls