Backshift 1.40 released

[Dan Stromberg]

I tagged 1.40 this morning - it was probably a little overdue.

Here are the most relevant changes:

Nov 1, 2018 - 1.40:

    New interpreters:

        Added CPython 3.7

        Added pypy 5.10.0 and pypy3 5.10.0

        Added pypy 6.0.0 and pypy3 6.0.0

    No longer supported interpreters:

        Jython 2.7.0; it's legacy python and had a bad bug

        Python 2.5 and 2.6

    Security fixes:

        Create save directory (via --init-savedir) with mode 700, owner=rwx, group=---, world=---

    Bug fixes:

        Fixed a rare traceback when a symlink disappears

        Fixed some inconsistent returns

        Verbose output no longer gives traceback for nonunicode filenames on Python 3

    Minor improvements:

        Progress moderate when on a tty

        Put rolling_checksum_pyx_mod in $prefix/lib/backshift/. not site-packages directory

        Improved some error messages a little.

        Tests no longer require Python 3

        ./configure script smarter about what it recommends for performance