Issue Summary

When clicking on a zip file in Trello attachments you used to be able to see a preview, which would show the contents of a zip file. Now when you click on a zip file it shows that preview is not available. 

Steps to Reproduce

1. Go to a Trello card
2. Attach any zip file
3. Click on it in the attachments part of the card

Expected Results

The preview of the contents of a zip file would be displayed.

Actual Results

You see a message that preview is not available and a link to Download the file.

Workaround

Downloading the file on your device and unzipping it works. 

Yet it is not a very handy option if you want to preview the file before downloading it to see if that is the correct file.