SConstruct: boost is no longer required
SConstruct: Remove tab
Fix so that builds work without python
Add ExactSegmentGraph and enable different fill rules for polygon_csg
Merge branch 'master' of github.com:otherlab/geode
fix offset_mesh overloads
quadric class
pull quadrics out to separate class
add empty()
do tilting offset only if angle > 0
add improve_mesh function
wrap improve_mesh function
Merge branch 'master' of github.com:otherlab/geode
SConstruct: Two tweaks

1. Let files() ignore entries of the form a/b.
2. Don't build latex if we don't have latex.
python/numpy: Check that numpy has been imported before use
erase_isolated_vertices and valence
more granularity for quadrics
improve_mesh works, but cannot add vertices
Merge branch 'master' of github.com:otherlab/geode
SConstruct: Don't use qt if it doesn't exist