Refactored Bento initialization; cleaned up more smelly code

All bento.box objects are now named and stored in bento.boxes object.
Bento now accepts a second argument `boxes` to auto init boxes upon
construction.  Cleaned up Box constructor and box.configure workarounds
by properly using .once and clever timing of "initialize" events via
process.nextTick
Bump to version 0.2.0

Bento is really cleaning up; very little code smell remains for
existing features.