Set up Sonatype Account

* Sign up for a Sonatype JIRA account [here](https://issues.sonatype.org)

To push a release version

1. Make sure the team agrees that it is time to release.

If you experience failures, you may need to:

- repeat the clean step above

- remove the temporary directory created to store docs by running `rm -rf tmp_gh-pages`

6. Run `utilities/finalize_release.sh`.

This script will release the staged artifact on the Maven Central Repository and push the README.md and gh-pages updates to github.

9. Create and merge in another PR to reflect the updated project version. For an example of what this PR should look like, see [#227](https://github.com/GoogleCloudPlatform/google-cloud-java/pull/227).

To push a snapshot version

Pushing a snapshot is completely automated. If "-SNAPSHOT" is included in the version denoted by the base directory's pom.xml, then an updated artifact will be pushed to the snapshot repository when Travis CI successfully completes a non-PR build. The build triggers the `after_success.sh` script, which handles the release process for SNAPSHOT versions.

Improvements

Automatic tagging is not currently implemented, though it was discussed in [#119](https://github.com/GoogleCloudPlatform/google-cloud-java/pull/119). If the version updates continue to be manual, a one-line git tag command can be added to `after_success.sh` to correctly tag releases. However, automatically creating useful annotations for this tag will be difficult. Also, if the release process becomes fully automated, tagging becomes a harder problem, as mentioned in that issue.