(fix) - ensure correct unmount

[JoviDeCroock]

Fixes: #1632
Adds a test for the wrong dom scenario (isn't fixed yet) but I aim at doing this in the future

[coveralls]

Coverage remained the same at 99.778% when pulling b973c40 on fix/unmount into 9ead713 on master.

[JoviDeCroock]

Hmm, with the changes from @andrewiggins this change does not seem to be needed... Anyone sees a scenario where we should at it for safety?

[marvinhagemeister]

That's awesome! Even if the original issue is shady fixed by other changes in master I'd love to merge the Test cases in this PR. They seem to valuable not to have 👍

[JoviDeCroock]

@marvinhagemeister would you like me to revert the change and just PR with the tests?

[andrewiggins]

I say let's check this PR as is. After working on my last PRs, I don't think_lastDomChild should be used as proxy for determining if something is Fragment. Since all Components are Fragments now, we should directly check the type (i.e. typeof vnode.type === 'function') or the presence of _component for behavior like this.

[andrewiggins]

I went ahead and merged this cuz I'm building on top of it for my next PR