build: run webpack on travis to catch any build failures during ci

Author: dpopp07

.travis.yml

@@ -6,6 +6,7 @@ before_install:
 - export DISPLAY=:99.0
 - sh -e /etc/init.d/xvfb start
 script:
+- npm run build
 - npm test
 - sed -i "s/\/master\//\/$TRAVIS_BRANCH\//g" README.md
 - npm run doc