Added decoder for chunked HTTP encoding

[sevzero]

This decoder will join up a HTTP response sent using chunked transfer encoding, raised in issue #168.

This is useful when attempting to extract files or gzipped responses sent using chunked transfer encoding, particularly when combined with the gunzip operation.

[mattnotmitt]

Hi @sevzero, thanks for the PR. master is currently frozen until #284 is merged; which introduces a new module format that hasn't been documented on the wiki yet, but if you have the time, you can branch off esm and using the already written operations as a guide, port this feature. Additionally, if you need a hand you can join our gitter where we'd be happy to help.
Also, before this is merged you'll have to sign the CLA for this project.