Make Liu layout throw exception when vertex with degree > 4 is found
Merge branch 'master' of https://github.com/bxt/smooth.git
Move Liu algo into own package and factor inner classes out
Add a stateful class for Ipe drawing and some convenience methods
Fix a bug in the positioning in Liu layout
Add SE and XY pair types
Add some utilities to the Port class
Make the test graph 4-planar
Test the Liu layout with an ipe drawing