Update coverage, add CI verbosity

Author: Ryan P Kilby

.travis.yml

@@ -13,10 +13,10 @@ env:
   - DJANGO="django>=1.8.0,<1.9.0" REST_FRAMEWORK="djangorestframework>=3.5,<3.6"
   - DJANGO="django>=1.8.0,<1.9.0" REST_FRAMEWORK="djangorestframework>=3.4,<3.5"
 install:
-  - travis_retry pip install -q $DJANGO $REST_FRAMEWORK "coverage==3.7.1"
+  - travis_retry pip install -q $DJANGO $REST_FRAMEWORK coverage
   - pip install .
 script:
-  - coverage run manage.py test
+  - coverage run manage.py test -v 2
   - coverage report
 after_success:
   - bash <(curl -s https://codecov.io/bash)