[0.4.0] Upgrade to dbt v0.20

[jtcohen6]

(same basic story as https://github.com/fivetran/dbt_hubspot_source/pull/46)

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 dbt version in integration tests, and remove dbt version requirement from integration tests dbt_project.yml — this will just use the dbt version requirement in the packages it depends on

Does this PR introduce a breaking change?

• [x] 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]
• [x] 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 - [x] Postgres - [ ] Databricks - [ ] Other (provide details below) I ran this on Postgres, everything passed, with one tiny change: I needed to wrap quotes around the `default` column in `brand_data`, since `default` is a reserved word in Postgres. ``` dbt deps dbt seed dbt run dbt test ``` As before, 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. **Provide an emoji that best describes your current mood** 🕴️ 🕴️

[jtcohen6]

I realize I accidentally included an edit to integration_tests/data/brand_data.csv that wrapped a column named default in quotes. This was needed to run integration tests on Postgres locally, but it doesn't make sense to include as part of this PR.