Add tar/gz/bz2 to Valid Attachment Types

[bsdgooch]

I noticed that the .zip filetype is supported as an attachment. Can we add these common filetypes to the list of valid attachments: .tar, .gz, .bz2 (and possibly others)?

It's common to share source code (and other filetypes) using these formats.

It was a great move to implement forums for the FreeBSD community, Thanks!

[danger@]

I have added a few filetypes into the allowed list, including the ones you have requested.