Prepare release v0.9.1 (#52)

Prepare release v0.9.1, a very minor one including #50 and #51, but also
to keep the gem's latest release somewhat fresh. No functional changes.

Prepare release 0.9.0 (#45)

I just noticed that we've had an unreleased change sitting in `master`
since December since changes in this gem are pretty rare unfortunately.
Let's cut a release just so we can get that change (#39) finally shipped
out.

Prepare release 0.8.0 (#37)

Prepare release 0.8.0, mostly containing the changes in #32.

Prepare release v0.7.0 (#30)

Prepare v0.7.0, containing largely the changes in #28 that add support
for past path unique job insertion.

Prepare release 0.6.1 (#27)

Prepare release 0.6.1, containing the Ruby gem fix from #26.

Prepare release 0.6.0 (#25)

Prepare release 0.6.0, which starts validating that advisory lock
prefixes fit inside of four bytes.

Prepare release 0.5.0 (#23)

Prepare release 0.5.0, which now validates tags and adds a `metadata`
property to inserted jobs.

Prepare release `v0.4.0` (#15)

Prepare release `v0.4.0`, which largely contains #14 which implements
the FNV hashing algorithm and drops the dependency on the `fnv-hash`
gem.

Prepare release `v0.3.0` (#11)

Prepare release `v0.3.0` which largely includes unique jobs from #10.
Also tweak the publishing instructions, which were once again, still
somewhat wrong (building a gem doesn't lead directly to an updated
`Gemfile.lock`).

Prepare release for `v0.2.0` (#6)

Updates gemspecs for `v0.2.0`, and also fixes up the gemspec update
script and release instructions as we iron out this whole process.