RELEASING.md

1. Update to the latest SDK versions in package.json and android/build.gradle.
2. Update version in package.json.
3. Add an entry to CHANGELOG.md
4. git commit -am "Preparing for version x.y.z"
5. git tag x.y.z
6. git push origin master && git push --tags
7. Create a new release in github and upload
8. npm publish