Just bumped the gem version

The gem version was not updated before the last release, so it's done at this time.

Breaking change: extend Module instead of include

This introduces a breaking change. Workers should extend Cuniculus::Worker rather than include Cuniculus::Worker from now on.

Even though this is a breaking change, I'm still bumping the minor version, and not the major version, since the library hasn't been tested in production enough to warrant a version >= 1.0.0. Until that point is reached, breaking changes can be expected.