Contours unreliable on deep crevices

[carter2422]

When working on a mesh with deep crevices Contours has a hard time finding the correct surface points: http://cl.ly/OzKB

Increasing the vert count has no affect on the result.

[patmo141]

This is partially related to the irregular vert spacing issue, however this will alwasy be a problem until we implement feature detection.