Spark On K8S 0.3.0

What's Changed

• feat: support driver and executor node selectors by @hussein-awala in #10
• feat: support driver and executor labels and annotations by @hussein-awala in #11
• feat: support driver pod tolerations by @hussein-awala in #12
• feat: support executor pod template path by @hussein-awala in #13

Full Changelog: 0.2.3...0.3.0