example usage in the commentary
Small change to subgraph-print

Multi-word labels now OK.
Augmented docstring for subgraph structure
an example from Tom
simplify graph-dot's attributes and printing
Merge branch 'master' into gh-pages

Conflicts:
	graph-dot.lisp
update
an example from Tom
simplify graph-dot's attributes and printing
Merge branch 'master' into gh-pages