Package tidy up

[jtcohen6]

Copied from dbt-labs/segment#42

Repo checklist:

• A license
• Issue and PR templates (as of Ready for 0.9.0: all-around upgrade #79)
• A codeowner (as of Ready for 0.9.0: all-around upgrade #79)
• The hub URL listed on the repo
• If relevant, a note in the README saying this package is not actively supported
• Installation instructions, including:
  • Link to packages docs
  • Variables that need to be included in the dbt_project.yml file
  • Listed database support
• A link to our package contribution guide (as of Ready for 0.9.0: all-around upgrade #79)
• A require-dbt-version parameter in the dbt_project.yml
• Models are documented
• Macros are documented (as of Ready for 0.9.0: all-around upgrade #79)
• Integration tests
• Move model logic intro model files, rather than entirely in adapter macros
• A Zap to the #package-releases channel in dbt Slack