[0.4.0] Upgrade to dbt v0.20

[jtcohen6]

Are you a current Fivetran customer?
Jeremy Cohen, dbt Labs, yes!

What change(s) does this PR introduce?

• Require fivetran_utils: [">=0.2.0", "<0.3.0"]. Lower + upper since you have full control over this package, and can release it whenever you need.
• Require dbt >= 0.20.0. Just a lower bound because we can rely on dbt_utils (via fivetran_utils) to hold the upper dbt bound for us.
• Bump project version (cosmetic only)
• Bump required dbt version for integration tests

Does this PR introduce a breaking change?

• Yes (please provide breaking change details below.)
• No (please provide explanation how the change is non breaking below.)

Is this PR in response to a previously created Issue

• Yes, Issue [link issue number here]
• No

How did you test the PR changes?

• CircleCi
• Other (please provide additional testing details below)

Select which warehouse(s) were used to test the PR

• BigQuery
• Redshift
• Snowflake
• Postgres
• Databricks
• Other (provide details below)

I ran this on Postgres, everything passed:

dbt deps
dbt seed
dbt run
dbt test

Happy to run against the other warehouses if you'd like. With an update like this, if the package parses/compiles/runs right on one, it ought to across the board.

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[fivetran-joemarkiewicz]

Thanks again for all your help @jtcohen6 in helping make our packages compatible with dbt v0.20.0. Your updates look good on my end and they work on my BigQuery dataset. I just updated the base branch to merge to feature/jcohen-dbt20-compatibility so we can ensure these updates pass our cross database Circle tests before merging and releasing.

I will tag you in the corresponding PR and call out if I encounter any hiccups across the databases. 💯

[jtcohen6]

Thanks @fivetran-joemarkiewicz! I'm going to open a PR for zendesk_source now. As soon as hubspot_source v0.4.0 is on the Hub site, I can also send over a PR for the hubspot package.