[feat] output progress on `aws cloudformation wait`

Several CI/CD environment e.g. Travis check for hanged executions based on stdout output, or the lack of it actually. Travis in particular has [a way to extend the timeout](https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received), but that is a workaround, not a solution.

Deploying an API Gateway or a CloudFront instance can take a really long time, and `aws cloudformation wait` does not output anything at all.

Please consider changing the current behaviour, or add a flag e.g. `--progress` that would print something to stdout every 30s=poll. A dot. A "Waiting for change-set to reach status CREATE_COMPLETE..." on a new line. Something.