Resume streaming `begin deploy` updates

[ryanblock]

During begin deploy we currently output the following message: (You can now exit this process and check in on its status with begin app deploy --status)

If you do that, you'll just get a status update for the latest deployment of your environment, but no streaming updates like what you'd normally get when running begin deploy.

It would be nice to resume those streaming updates after exiting the process, maybe with a command like begin deploy {env} --tail or --resume or something.