net/py-kafka-python: Update to 1.3.4

Remove devel/py-six dependency, it was incorporated upstream in v1.3.0.
While here, add LICENSE_FILE and set architecture neutral.

Changes: https://github.com/dpkp/kafka-python/blob/master/CHANGES.md#134-aug-13-2017

PR: 221959
Submitted by: Sergey Akhmatov <sergey@akhmatov.ru>
Approved by: Christer Edwards <christer.edwards@gmail.com> (maintainer)