Spire 0.9.0 release announcement

[Erik Osheim]

Hello Spire friends,

I'm writing to announce the release of Spire 0.9.0. This is a
substantial release that contains many bug fixes and performance
improvements.

Most notably, 0.9.0 contains:

* A first pass at lattices, semilattices, and Heyting algebras is
included. The API should be relatively stable but some changes may
occur before the nex trelease.

* An improved inveral implementation: intervals are faster, more
powerful, and have fewer bugs thanks to Denis Rosset.

* Better checked arithmetic macros. Tom Switzer and I made the
existing Checked macros more efficient and also more flexible.

(A full list [1] of changes is available.)

A follow-up release, 0.9.1, will contain work on groupoids and partial
algebras by Denis Rosset, as well as any bug fixes that are
needed. I'll email this list again with a longer-term road map.

Thanks to Spire's contributors and users for making this release possible!

-- Erik

[1] https://github.com/non/spire/blob/master/CHANGES.md#version-090