Fixed another bug that prevented the extension from working at all.

Allow click on image/attachment in an email to open in a new tab, which is the original Salesforce behavior.

Before, this navigated away from the Salesforce tab, to a page with the image/attachment, which is not the desired behavior. And this forced the user to explicitly navigate back to the Salesforce page.

Fixed bug that prevented the extension from working at all.

Restrict to *.force.com* URLs only. This allows opening files in Saleforce in a new, separate tab. (The assumption is that one does not want to force these into the Salesforce tab.