thought-machine/please v1.4.9

Please v1.4.9

on GitHub

First release available on the public github repo.

• plz clean now backgrounds itself when possible, in which case the user can
  continue with other tasks with no delay.
• Added licenses() builtin function for Bazel compatibility; it roughly parallels
  theirs in setting the default licence for all targets in a BUILD file. Implicitly
  we can also now use package(default_licences = [...]) which is equivalent.
• + is now allowed in names of build rules.
• Fixed .deb package to include plz_diff_graphs.