Switch to WebdriverIO browser tests

[christian-bromann]

This project currently seems to use Karma for their browser tests. Today WebdriverIO has its own browser runner that allows to run Unit and/or component tests in the browser, locally or on Sauce.

I am happy to take a stab at updating the test setup to run browser tests in WebdriverIO.

What do you think?

[afcapel]

@christian-bromann the current setup is rather flaky, any improvement to it will be welcomed.