Add disable progress bar option

[aflag]

While it's nice to have a progress bar when executing twine interactively, it would be nice to have the option of not displaying the progress bar for those of us who want to redirect twine's output to a file or otherwise use it in a non-interactive way. tqdm has a disable flag: https://github.com/tqdm/tqdm#documentation so it should quite simple to implement.

[sigmavirus24]

I would happily merge a PR implementing this.

[varunkamath18]

I am interested in making this change if no one else has picked it up.

I checked out the source quickly and I might be wrong but it appears that the following changes will be required:

• Create new boolean argument in settings.py.
• repository.py needs to forward the disable flag to the tqdm ProgressBar.
• There are several ways to send this flag over to the ProgressBar, quickest and the dirtiest being adding the flag to the upload method in the Repository.

Since the ProgressBar is a small part of upload I think it is not that big of a deal to include a disable_progress_bar option in the upload method. We could also expose it in the Repository init if it makes sense.
I don't see any other arguments of tqdm that might need exposing through the command line in the future other than maybe the leave flag which removes the traces of the progress bar upon completion. However, I don't foresee a case where this flag might be needed.