Also process certificates with the .crt extension.
Also process certificates with the .crt extension.

The [official Docker docs on creating a self-signed certificate](https://docs.docker.com/registry/insecure/#using-self-signed-certificates) use a `.crt` extension for the public PEM certificate. To help users that are following those documents, it would help to also accept that extension in this script, as well.
qxo/boot2docker,SvenDowideit/boot2docker,whuwxl/boot2docker,qxo/boot2docker,SvenDowideit/boot2docker,whuwxl/boot2docker,boot2docker/boot2docker,power-dev-env/boot2docker,tianon/boot2docker-legacy,power-dev-env/boot2docker