Pip install without progress bars

Use pip config to turn these off by default:

pip config --user set global.progress_bar off

(perhaps remove --user for admins, or use replace with --venv for virtualenv)

That PR was merged and is available on the latest stable build (pip 10.0.1 at the time of writing). Just do:

pip install foo --progress-bar off

Other args are available. See the pip install docs.