Write better tests

[maxkueng]

Test more stuff more extensively

[jbraithwaite]

Hey Max,

Tests are timing out, maybe consider using Sinon (or something similar) to fake http requests?

[maxkueng]

Thanks @jbraithwaite! I know... I even already give mocha 10 seconds for each test and they still time out.
But yes, it's not the idea to test MusicBrainz's endpoint too. I just currently don't have time to make it better. Thanks for the tip about Sinon. I'll check it out. I had previously stumbled upon echoecho. I'll have a look at both.