1.4.0 release date

[Olly Betts]

The 1.3.7 release tarballs are currently being built (though I think
I'll go to bed rather than wait for them, so it probably won't be
uploaded today).

1.3.7 is essentially a release candidate for 1.4.0 - please test
with it and report any issues you hit.

Unicode 9.0.0 is due to be officially release on June 21st, and it
seems worth including, so unless there's a show stopping bug found
which we can't fix in time, my plan is to release 1.4.0 on or shortly
after the Unicode release - i.e. in about 3 weeks time.

I've prepared a patch to update to Unicode 9.0.0, but haven't included
it in 1.3.7 as Unicode say "No products or implementations should be
released based on the beta UCD data files".  While it could perhaps be
argued that 1.3.x aren't releases, wider testing of the Unicode table
update doesn't seem likely to uncover any issues.

Cheers,
    Olly