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

It's occasionally useful to see at a glance when releases were pushed to understand what release might have caused a customer's issues. This back-fills dates for the last few months of releases and sets a precedent that can be followed in the future.

update buildpack tests to expect success for all 2.7.15 builds

Add a Pull Request template

To try and help prevent the notification noise from PRs being opened
against upstream by mistake.

v 138 changelog

Update SQLite3