worked on implementing basic PDA functionality
refactored automata eval use generic transition
a more generic transition return type is now supported
transition behavior is now more facilitated by the evalstream functions
the transition function is more for describing the transition to evaluate
updated evalstream fastforward and rewind functions
created full implmenetation for pfa_transition_func
evalstream functions now take the automata as a parameter
the transition_func is now just for generating a change for the evalstream to apply or revoke