Google Code-in

Let's add a travis build that ensures the code quality of our website is up to our standards.

Proceed as follows:

• create a .travis.yml file, you can look at our other modules for inspiration
• in the travis build, install and run jshint: https://www.npmjs.com/package/jshint
• in the travis build, install and run a css linter, eg: https://www.npmjs.com/package/stylelint
• in the travis build, install and run an HTML linter, eg: https://pypi.org/project/html-linter/
• send a pull request