Nested transactions
Parent transaction subscribes to child states to go back to open
Support for open transactions
Send query events to the parent.
Working nested transactions
begin refactor of transaction

also add another test for nested transactions
refactor Transaction, update docs

Transactions now have 4 states (disconnected, connected, open, and closed)
instead of ~6. The StateMachine base class has also been simplified (removed the
'errored' psuedo-state and replaced the method-swapping with __proto__ swapping).
Merge branch 'piethis-nested-transactions'