0.12.0

Changelog

• Update pipelines command to reflect changes in the API (#304, #308, #317, @mukulmurthy, @rgovind3, @aakash-db)
• Add support for cluster policies (#303, @itaiw)
• Add tokens command to expose the tokens API (#246, @areese, @andrewmchen)
• Add support for --cluster-name or --cluster-id to clusters commands (#313, @areese, @andrewmchen)
• Add pipelines run and stop commands (#323, @calving-db)
• Add retries with exponential backoff on 429 HTTP responses received from the DBFS API (#319, #326, @gotibhai, @bogdanghita-db).
• Improve error message on JSON errors (#320, @aakash-db)
• Hide token on databricks configure input (#312, @areese)
• Upgrade linters for py36 build (#307, @andrewmchen)