Lint and build frontend in Travis.

This adds an ESLint step to the CI service so we prevent unlinted code from
making its way in. It also runs the frontend build as a smoke test.

Author: CM Lubinski

.travis.yml

@@ -9,10 +9,19 @@ env:
 cache:
   directories:
     - ~/.cache/pip
+    - ~/.nvm/nvm.sh
 install:
  - pip install tox
+ - curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.2/install.sh | bash
+ - source ~/.nvm/nvm.sh
+ - nvm install --lts
+ - nvm use --lts
+ - npm install
+ - bower install
 script:
  - tox -e $TOX_ENV
+ - gulp lint
+ - gulp build
 notifications:
   slack:
     rooms: