Docker Edge recently shipped with a -rc2 docker-compose, which did not pass version comparisons in ddev so was not functional with ddev. The only user-visible change in this release is to solve that problem.
Please read the release notes for v0.15.0 if upgrading.
Installation/Upgrade
See the instructions but it's easy: macOS Homebrew: brew upgrade ddev. Linux or macOS via script: curl https://raw.githubusercontent.com/drud/ddev/master/install_ddev.sh | bash. Or anywhere, including Windows, by just downloading the tarball or zipball and placing the executable in your path where it belongs.