Merge growthring-web into parent; add xsbt-web-plugin
Update docs
Gap parameter
Mention graphviz
Use BitSet instead of Set[Int] for speedup
Remove print
Link jar ver 0.4 instead of 0.3

Follows-up: a468043e31073c80a9c58746c808890ae439d66f
Default arguments and warnings
add segment mode
Add pattern for boundary
Comments
Change reduce(_++_) to flatten for speed-up