Add `--quiet` option to supress progress output

[patrickfreed]

swiftly currently produces progress output when downloading to give the user an idea of how long an install will take. This is ideal for humans using it via the CLI, but it can be pretty noisy when included in the logs of a CI test run. We should provide a --quiet argument that suppresses this output for such uses cases. Error and possibly success output would still be produced.

We probably would want to enable this for swiftly's tests too.