Add browser tests on TravisCI

[gartz]

Proposal

Add browser tests on TravisCI, need to research how to do that, and how to configure Karma to be compatible.

A code I've found in another project might help:

  // This block is needed to execute Chrome on Travis
  // If you ever plan to use Chrome and Travis, you can keep it
  // If not, you can safely remove it
  // https://github.com/karma-runner/karma/issues/1144#issuecomment-53633076
  if(configuration.browsers[0] === 'Chrome' && process.env.TRAVIS) {
    configuration.customLaunchers = {
      'chrome-travis-ci': {
        base: 'Chrome',
        flags: ['--no-sandbox']
      }
    };
    configuration.browsers = ['chrome-travis-ci'];
  }