Add instructions for releasing slow_cooker (#44)

RELEASE.md

@@ -0,0 +1,41 @@
+# Releasing slow_cooker
+
+Once all of the branches for the release have been merged and the CHANGELOG.md
+file in master has been updated to describe the new release, use these
+instructions to publish the release to Github and Dockerhub.
+
+## Github
+
+Start by running `./release.sh` to generate the binaries that will be attached
+to the release.
+
+Next [create a new release](https://github.com/BuoyantIO/slow_cooker/releases/new)
+on Github.
+
+* For the version, enter the numeric release version.
+* For the title, also enter the numeric release version, or something snappier.
+* For the description, copy over the entire CHANGELOG.md entry for this release.
+* For the binaries, attach all three binaries from the `./release.sh` script.
+* Then click "Publish release"
+
+## Dockerhub
+
+Next build and push the docker images to Dockerhub.
+
+First build and push the versioned image (replacing `<release-version>` with the
+actual numeric release version that you are releasing):
+
+```bash
+$ docker build -t buoyantio/slow_cooker:<release-version> .
+$ docker push buoyantio/slow_cooker:<release-version>
+```
+
+Then update the image that's tagged as `latest` to match the new release:
+
+```bash
+$ docker tag buoyantio/slow_cooker:<release-version> buoyantio/slow_cooker:latest
+$ docker push buoyantio/slow_cooker:latest
+```
+
+Check the Dockerhub [tags page](https://hub.docker.com/r/buoyantio/slow_cooker/tags/)
+to make sure that the new release tag shows up.