Modifications of instance attributes now affect payload.

Add block_until_empty

Reduce redundant specification of arguments

Fix version issue.

Remove old google dependencies and add support for polling.

Dropped AppEngine support. No more base64 encoding. AWS_DEFAULT_REGIO…

…N support. Moved queue_name to the front of the arguments list.

Removed broken features

Added kwargs support for RegisteredTask

LocalTaskQueue w/ multiprocess support

Updated CloudVolume credentials semantics