Upgrade dbt-utils v0.7 (dbt-labs#67)

* Upgrade dbt-utils v0.7

* Update version, company name

Merge pull request dbt-labs#60 from fishtown-analytics/0.18.0

Bump dbt to v0.18.0

Merge pull request dbt-labs#58 from fishtown-analytics/bump-utils-0.5.0

Bump utils 0.5.0

Update readme

Merge pull request dbt-labs#45 from fishtown-analytics/refactor/check…

…list

Refactor/checklist

Merge pull request dbt-labs#38 from fishtown-analytics/fix/null-sessi…

…on-number

Fix null session numbers

Merge pull request dbt-labs#29 from fishtown-analytics/refactor/quali…

…ty-of-life

Refactor/quality of life

Merge pull request dbt-labs#22 from fishtown-analytics/feature/user-s…

…titching-fields

Add extra fields to segment_web_user_stitching

Merge pull request dbt-labs#21 from fishtown-analytics/feature/referr…

…er-mapping

Map referrer fields to medium and source

Merge pull request dbt-labs#19 from fishtown-analytics/feature/pass-t…

…hrough-cols

Add variable to pass extra columns through the package