Improve finite state machine

[otabuzzman]

XState JavaScript state machines and statchars

[otabuzzman]

• [x] put actions of state transitions tighter together.

[otabuzzman]

• model composite states with
  elements in DOM.
• store current event in data attributes in surrounding composite-div (e.g. for later use in C state).
• store current state in outermost non-ambiguous surrounding composite-div (e.g. for use by H state).
• clear data attributes after use by C or H states.