Allow the submitter to include attachments

[CelticMinstrel]

I'm aware that this is currently impossible to implement using the GitHub API for manipulating issues, but it might be possible to do in other ways - for example, creating gists of text attachments and uploading non-text attachments to either GitReports or some external server.

[CareyJWilliams]

The easiest solution here would probably be to ride on the back of some third-party pastebin, but that raises a few issues, most importantly those of security and dependability (long-term persistence, uptime). Still, I'd be quite keen to see this functionality, if anyone has any leads.