Build sphinx docs on travis quietly

.travis.yml

@@ -22,7 +22,7 @@ before_script:
   - psql -c 'create database test_aisdb;' -U postgres
 script:
 - python setup.py test
-- travis-sphinx --source=docs build
+- travis-sphinx --nowarn --source=docs build
 after_success:
 - if [[ "$COVERAGE" == "true" ]]; then coveralls || echo "failed"; fi
 - travis-sphinx deploy