Release of datafu-spark 1.8.0

[Eyal Allweil <ey...@apache.org>]

Hi all,

This is just a heads-up that I am planning on releasing our next version.
You can see the changes in changes.md, but I'm copying them to here too:

*** dedupWithCombiner method now supports a list of columns in the order /
group by params  (DATAFU-171)
* Scala Python bridge now uses secure gateway (DATAFU-167)
* Spark 2.2.0, 2.2.1, and 2.3.0. no longer supported

I'll send an official release/vote email as soon as it's ready. I think
after this release we shouldn't try (necessarily) to make releases
compatible with the Spark 2.4.x line, but instead release for Spark 3.x as
soon as possible.

Regards,
Eyal