[Checkins] [zopefoundation/grokcore.json] eefbb7: update buildout extends URL to the 3.0.0a1 tag

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/grokcore.json
  Commit: eefbb7767587f59049c777f5b872b140a65b1f96
      https://github.com/zopefoundation/grokcore.json/commit/eefbb7767587f59049c777f5b872b140a65b1f96
  Author: Jan-Wijbrand Kolman <jkolman at minddistrict.com>
  Date:   2018-01-22 (Mon, 22 Jan 2018)

  Changed paths:
    M buildout.cfg

  Log Message:
  -----------
  update buildout extends URL to the 3.0.0a1 tag