[test] Ignore stack lines from outside our test code

[cspotcode]

Splitting #40 into multiple PRs for easier review.

This stops the tests from breaking with Node.js updates.

[AndreasMadsen]

This makes the test too relaxed. It was this way a long time ago, but there are some bugs related to removing lines that this won't test for.

[cspotcode]

Ok, would you like a PR that fixes failing tests by updating them for node v11, the version being used by the TravisCI tests?

[AndreasMadsen]

Sure, we can do that. I don't care that much about a green TravisCI myself. I just use git diff as a sanity check that things are good.