Release v1.4.1 for the deadlock of issue #4.

Add a new public API to group Deferreds and preserve their order.

Release v1.3.3.

Release 1.3.2.

Release v1.3.1.

Release v1.3.0.

Release v1.2.0.

Change-Id: Ie4d2be7df718bdb70562d15468b2c5a01ece8eda

Release v1.1.0.

Change-Id: Id3142f69074ceaebc7f190e861dd7e2dad55b21f

Optimization: don't wait on a Deferred already in State.DONE.

When a Callback returned a Deferred already in State.DONE, the current
Deferred was paused and immediately resumed, which involved the creation
of an unnecessary Continue callback and other objects.  We now bypass
this entire code path, which helps in the cases where a Callback returns
a Deferred built with Deferred.fromResult or Deferred.fromError, or if a
real Deferred completes so quickly that we directly see it in State.DONE.

Change-Id: I710266e05b5f37d676018f706c923ecafa276ffc