Bug in contour tree, causing segfault.
Self-implemented hidden nodes.
Merge branch 'master' of https://github.com/eldridgejm/denali

Conflicts:
	gaussian_complex.off
	src/contour_tree.cpp
	tests/pydenalitest.py
Merge branch 'master' of https://github.com/eldridgejm/denali
Normalizing height is squashing figure, reverted.