Release notes

#Features

• Add v3.8 schema support
• Add missing test dependency ddt to setup.py
• Add "--attach-dependencies" to command "up" for attaching to dependencies
• Allow compatibility option with COMPOSE_COMPATIBILITY environment variable
• Bump Pytest and add refactor compatibility with new version
• Add docker context support

#Bugs

• Sync compose-schemas with upstream (docker/cli)
• Remove None entries on exec command
• Force MacOS SDK version to "10.11"
• Add python-dotenv to delegate .env file processing
• Enforce Python37 in the creation of virtualenv on windows CI
• Don't adjust output on terminal width when piped into another command
• Show an error message when version attribute is malformed