add document.
improve directory structure.

remove .gitattributes
update .gitignore
update pom.xml.

add zkclient dependency
add annotation support for spring.

update .gitignore
add zkEventHandler(will be invoked when zk event was triggered)
add zkContext for managing beans(with @ZkManage) and fields(with
@ZkValue)
add FieldEditor for fields modification(will change the field's
accesible state)