added jsFlow

Hello I want to add my `jsFlow` library here. It's a fork of jWorkflow with a lot of enhancements and new features. It uses the original design of defining flows by extending it for more use cases like dynamic flow execution and state machines.

It's still a very small library ( which is one of it's goals ). 

The library has following size stats:

Core (without state machine factory helper) 
Normal 6.1KB
Minified 2.3KB
Goolge Gzip ~0.9KB 

Full:
Normal 7.3KB
Minified 2.9KB
Goolge Gzip ~1.8KB