compatibility with dbt config-version update

• update package to compatibility with dbt config-version: 2
  as discussed in: dbt-labs/dbt-core#2655

postgres_utils w/ optimizers

• Add acknowledgement to fishtown-analytics project postgres
• index macro tested and verified with dbt 0.17
• uindex macro tested and verified with dbt 0.17
• initial documentation (to be expanded)