dbt: snowplow 0.13.0

🚨 Breaking changes

• This package now requires dbt v0.20.0 and dbt-utils v0.7.0. dbt v0.20.0rc2 is currently available as a release candidate. If you are not ready to upgrade, consider using a previous version of this package.
• This package depends on dbt-labs/dbt_utils. If the latest version of another installed package depends on fishtown-analytics/dbt_utils, you'll need to wait to upgrade. See discourse for details.

Under the hood

• Reorganize integration tests (#99)
• Use new adapter.dispatch syntax (#104)