Use js-atom internally for state

[glenjamin]

And also remove & document that the react-style automerging of objects doesn't happen. This is so we can support any type of object here without messing it up.

Possibly worth providing another util on the devboard module to do a clean state update? devboard.update(state, newProperties) which would be equivalent to Object.assign({}, state, newProperties.

could possibly expand this on the card param

• card.value - current value (with support for card.state as a back-compat fallback?)
• card.update() - atom.swap
• card.set() - atom.reset
• card.atom - the atom itself
• card.merge(obj | func) react-style shallow-merge update (with support for card.setState as a back-compact fallback?)