[release] pantsbuild.pants 1.5.0.dev1

[John Sirois]

The second dev release of the 1.5.x series is now available on pypi.

As usual, the release notes are available here: https://www.pantsbuild.org/notes-master.html

Thanks to the contributors in this cycle:

      5 Daniel Wagner-Hall

      4 Kris Wilson

      3 Benjy Weinberger

      2 Yi Cheng

      2 John Sirois

      1 Stu Hood

      1 Roger Jiang