a new example
some changes to d3adaptor to allow not specifying any node list
edge lengths test
Merge branch 'master' of https://github.com/tgdwyer/WebCola

Conflicts:
	WebCola/examples/unix.html
Fix automatic downward directed graph constraint generation

Quick and dirty fix for #14.
new link length api
Merge branch 'master' of https://github.com/Muon/WebCola into Muon-master

Conflicts:
	WebCola/cola.v1.min.js
	WebCola/src/linklengths.ts