Improve runtime performance

[imme64]

Running js2php in its PHP form (#14) shows around 75x slower performance compared to NodeJS version. Profiling the PHP code shows that the "get" function is called 5.6 million times and makes 28.1% of the time.
Member access could be implemented natively (without wrapper functions) and using __get(...) magic functions if the accessed property does not exist natively.
I would say that a performance factor of 20x should be possible and acceptable.