Update CONTRIBUTING.md

[merks]

Include a link to the Oomph setup.

[merks]

@fipro78

This adds the link to the contribution guide.

[merks]

Given this only changes a *.md file, the build failure seems not related. And this build passed:

#98

[fipro78]

@merks
Since the update of the target platform to a newer eclipse platform I see these test failures spawning sometimes. Looks like a concurrency issue that sometimes events are not fired when they should (at least in the test) and therefore the test fails. I have no idea why this happens since the update.

[merks]

I see. That’s very annoying and disconcerting. One can’t be sure if it’s a test case problem or a real framework problem.

[fipro78]

Yes, I am still searching for the cause. Hard to find because locally the tests succeed most of the time.