Add standardjs linter

.travis.yml

@@ -46,13 +46,16 @@ before_script:
 - curl -Lo geckodriver.tar.gz "https://github.com/mozilla/geckodriver/releases/download/${GECKO_DRIVER_VERSION}/geckodriver-${GECKO_DRIVER_VERSION}-linux64.tar.gz"
 - tar xzf geckodriver.tar.gz -C bin
 - PATH=$PATH:$PWD/bin
-script:
+- nvm install --lts
+- npm install -g standard
 - |
-  if [[ -z $DJANGO ]]; then
-    tox -e $TOXENV
-  else
-    tox -e py$(echo $TRAVIS_PYTHON_VERSION | sed -e 's/\.//g')-dj$DJANGO
+  if [[ -z $TOXENV ]]; then
+    export TOXENV=py$(echo $TRAVIS_PYTHON_VERSION | sed -e 's/\.//g')-dj$DJANGO
   fi
+- echo $TOXENV
+script:
+- tox -e $TOXENV
+- standard
 after_success:
 - coveralls
 deploy: