Add "AND CONTRIBUTORS" to options.py license

Add "AND CONTRIBUTORS" to options.py license

From https://groups.google.com/d/msg/bup-list/8lcxXuXilTE/JC9rm69oAQAJ

  From: Avery Pennarun <apenwarr@gmail.com>
  Date: Sun, 25 Mar 2018 21:35:58 -0400
  Message-ID: <CAHqTa-2LB2mqscnzZmmixeTbR86BPh=FTk3UyGQKjPwaQPrZ3g@mail.gmail.com>
  Subject: Re: bupsplit.c copyright and patching
  To: Rob Browning <rlb@defaultvalue.org>
  Cc: Robert Evans <evansr@google.com>, bup-list <bup-list@googlegroups.com>
  On Sun, Mar 25, 2018 at 1:48 PM, Rob Browning <rlb@defaultvalue.org> wrote:
  > Avery Pennarun <apenwarr@gmail.com> writes:
  >> On Sun, Mar 18, 2018 at 11:52 AM, Rob Browning <rlb@defaultvalue.org> wrote:
  >>> Avery Pennarun <apenwarr@gmail.com> writes:
  >>> So for the record, it sounds like you approve of changing the relevant
  >>> bupsplit.h and bupsplit.c phrase to this?
  >>>
  >>>   THIS SOFTWARE IS PROVIDED BY AVERY PENNARUN AND CONTRIBUTORS``AS IS'' AND ANY
  >>
  >> Yes, that's fine.
  >
  > And perhaps you'd approve of making the same change to options.py as
  > well?

  Good idea.  Let's do that :)

Signed-off-by: Rob Browning <rlb@defaultvalue.org>