promise4j v2.4.0

1. add Promise.create
2. add then Fulfillment
3. update Promise.all to allow reject.

promise4j v2.1.0

fix status spread, add ThenFulfillment.

promise4j v2.0.1

fix SingletonWorker.

promise4j v2.0.0

1. fix reject bug
2. add waiting sub status to allow only accept the first fulfill or reject.
3. add thenCatch to allow fix upstream exception.

promise4j v1.4.1

let cancel return if really canceled.

promise4j v1.4.0

add utils/SingletonWorker.

promise4j v1.3.0

add transform executor, add cancel.

promise4j v1.2.0

change package name to com.github.webee.*

promise4j v1.1.0

update then, add ClosureTransform, Runnable.

promise4j v1.0.0

the initial release.