Remove Ops macros in favor of Machinist.

Now that we are publishing the ops macros externally via Machinist,
it made sense to stop duplicating that code internally. Machinist
0.3.0 supports all the operator styles/names that Spire needs as
of now, and it will be easy to publish future changes as we need
them for Spire.

(We could also keep our own names map here, if we wanted to stop
relying on Machinist's DefaultOps class.)
Some README updates.
Update README documentation.
put a out-of-date warning in the GUIDE
add missing resolver
Setting version to 0.8.0
Setting version to 0.8.1-SNAPSHOT
disable scaladoc to allow release
Setting version to 0.8.1
Setting version to 0.8.2-SNAPSHOT
reenable scaladoc
Remove C-style comments to avoid triggering scaladoc bug.

This commit makes some slight changes to comments in Well*.scala.
These files were triggering a scaladoc bug under 2.10. The changes
were only cosmetic, no code other than comments was modified.
Setting version to 0.8.2
Setting version to 0.8.3-SNAPSHOT
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