Release v1.3.0

[flavorjones]

Cut a release, v1.3.0

• [x] Update CHANGELOG.md
• [x] Update README.md if necessary
• [x] Bump version in pkg/irc/irc.go
• [x] Commit and push.
• [x] Create a git tag and push it
• [x] make all to create a docker image
• [x] Tag the docker image, e.g. docker tag flavorjones/irc-notification-resource:latest flavorjones/irc-notification-resource:v1.1.0
• [x] make docker-push
• [x] Copy README to dockerhub overview
• [x] Create a github release with CHANGELOG snippet as description
• [x] Check that the resource works by kicking off the test-notification job

[flavorjones]

See https://ci.nokogiri.org/teams/flavorjones/pipelines/irc-notification-resource/jobs/test-notification/builds/7 for live test of v1.3.0.