update bob dependency to point to internal bob-builder fork

Added this for local testing because bob requires 2.7, should not be merged to master

Pin pip version used by pipenv

Add Apache Airflow 1.10 Support

Update travis setup for Hatchet

Fix Python 3.6 message when using Python 3.7

Fix indentation levels

more helpful messages about supported versions

Hatchet/yay

Start adding dates to changelog entries