afew: 2.0.0 -> 3.0.0

MailMover: many fixes

  Previously, MailMover didn't properly preserve flags when renaming files, and
  moved all mail to `cur`. This was fixed. Also, MailMover gained a test suite.

New filters: PropagateTags[ByRegex]InThreadFilter

  These filters allow propagating tags set to a message to the whole thread.

New command line argument: --notmuch-args= in move mode

  In move mode, afew calls `notmuch new` after moving mails around. This
  prevents `afew -m` from being used in a pre-new hook in `notmuch`.

  Now it's possible to specify notmuch args, so something like `afew -m
  --notmuch-args=--no-hooks` can live happily in a pre-new hook.

Python 3.4 and 3.5 support dropped

  afew stopped supporting the older python versions 3.4 and 3.5, and removed
  some more Python 2 compatibility code. (`from __future__ import …`, utf-8
  headers, relative imports, …)