Avoid memory copy when writing payloads in MessagePacker. https://github.com/msgpack/msgpack-java/pull/82#discussion-diff-12501690
Fixed to use ByteBuffer position and remaining values to specify dump range
Reuse flush() and set ByteBuffer position correctly after flushing
Fix typo
Merge pull request #87 from msgpack/v07-packer

Avoid memory copy in MessagePacker.writePayload