Update README for 0.8.2 and make REPL useful again.
Add CHANGES.md a change log for Spire.

I still need to try to backfill this from old release notes.

Hopefully we can keep this up-to-date as we move forward, to make
sure we can make accurate release announcements and avoid forgetting
to mention important changes (or credit someone's work).
make change log a bit more markdown-y
Merge commit 'ece8ef8f6492a15b788ebcb03dfcb7e754b9b0db' into topic/interval-point