WireIt version 0.2.1

I made a few updates this week-end. They mostly concern the Container
and Layer classes.

Here are the changes:

• new Layer.getWiring function to save the state of the wiring. It
  can be customized by overriding Container.getConfig
• jsBox updated to use the Layer.getWiring function
• no default width for containers so they can auto-adjust to the
  content
• Layer.addContainer and Layer.addWire now returns the created
  instance
• Added the method Container.redrawAllWires and
  Terminal.redrawAllWires
• Added Layer.removeAllContainers
• adds a “body” div to the container
• CSS updates on Containers and Layers
• adds a focus CSS class on the last mousedown-ed container in the
  layer
• bugfixes (events “addWire” and “removeWire” added to WireIt.Layer,
  offset in the connections)