Guard against colinear seed points

[debk1]

I've found this code very useful -- thank you. Surface reconstruction is out of my area of expertise so this comment might be invalid... I have found the need to guard against colinear points in findSeedTriangle. Otherwise it can return a seed triangle with normal()=nan

[bernhardmgruber]

Hi! Thank you for reaching out! I am glad you found it useful!

This implementation is intentionally kept simple so I am sure there are lots of quality bugs like the one you described. If I find some time, I can implement a quick fix, like enforcing a minimum for all angles in the seed triangle, or a minimum area, etc. Feel free to also propose a PR!