Bug 1061915 - Add link to badge awarded tweets

The various "I just got a badge" tweets were intended to include a link in them.  Because gmail (and likely other email clients) "helpfully" convert plaintext urls into anchors, the link needs to be left out of the "preview" in the email's textarea (since, after being helpfully converted, it would then appear as ugly, raw html in the textarea).

After figuring this out, I then forgot to include the link in the actual tweet contents as I had intended to.  Oops.  This fixes that oversight.