Add retry method

Add retry api for try call current step handler once again

Add BDD testing

start() can pass data to initial step.
destroy() stop anything and release private data in chain's scope.
BDD testing

Fix data method bug

data has old code result in error, it is my fault.

Refactor

1. Refactor, make the code more clear
2. Remove "filter","before","sham" methods, and use "destroy" instead of "stop"
3. Add "some" for one steps has multiple handlers and need only one to call chain.next()
4. Support call define multiple handlers in a "then" step, step over after each handler call chain.next()
5. No more support pass param in step handler, such as:

Chain(func, param).then(func1, param1)

add Chain sham supporting

0.0.3

version update to 0.0.3

Full feature impeletation and docs

Full feature impeletation and docs