Update release steps (#107)

Author: chris-mitchell

RELEASING.md

@@ -0,0 +1,16 @@
+Releasing
+========
+
+ 1. Change the version in the `gradle.properties` file to a non-SNAPSHOT verson.
+ 2. `git commit -am "Prepare for release X.Y.Z."` (where X.Y.Z is the new version)
+ 3. `git tag -a X.Y.X -m "Version X.Y.Z"` (where X.Y.Z is the new version)
+    * Run `git tag` to verify it.
+ 4. `git push && git push --tags`
+    * This should be pushed to your fork.
+ 5. Create a PR with this commit and merge it.
+ 6. Confirm the new artifacts are present in https://repo1.maven.org/maven2/com/dropbox/affectedmoduledetector/affectedmoduledetector/
+    * If the plugin fails to publish the release, you'll need to log into Sonatype and drop any repositories under 'Staging Repositories' and re-run the CI job to publish.
+ 7. Go to https://github.com/dropbox/AffectedModuleDetector/releases and `Draft a new release` from the tag you just created
+ 7. Update the top level `gradle.properties` to the next SNAPSHOT version.
+ 8. `git commit -am "Prepare next development version."`
+ 9. Create a PR with this commit and merge it.