Philipp Glock

There seems to be an error. If the tests are run on circleci, `test.js` can not connect to `localhost`. `test.js` should also fail if an unhandled promise rejection occurs.

[imagehash](https://github.com/JohannesBuchner/imagehash) is used. The test calculates the average hash for every generated image and its reference image. It fails if the difference of the hashes is larger than 10. The...