Algebird 2019 edition

This is a big release with many new features:

• many version update by @scala-steward
• many cleanups and build improvements by our Spotify friends and co-maintainers: @regadas @nevillelyh
• support for scala 2.13 #719
• drop support for 2.10
• Scan abstraction by @jeff-stripe #739
• support for building monoids and aggregators with shapeless by @non and @johnynek #655

v0.13.5...v0.13.6

Thanks to everyone who helped with this release! (including the above and @dieu @sritchie @alanbato )