We need to support rendering tests

[dirkschulze]

We need to support rendering tests to confirm that any change doesn't break behavior. I am not sure if GitHubs "rich diffs" can help.

Piwik takes screenshots and compares them with stored pixel results. Piwi uses a combination of Phantom.js and Travis CI. We should investigate ASAP.

[dirkschulze]

http://piwik.org/blog/2013/10/our-latest-improvement-to-qa-screenshot-testing/

[dirkschulze]

Some more links.

The screenshot API of Piwik:
https://github.com/piwik/piwik/tree/master/tests/lib/screenshot-testing

The Travis setup file:
https://github.com/piwik/piwik/blob/master/.travis.yml