add date for each feed entry's link, to match gemlog specs.

Hi!

This is a little patch (and I  guess not well written as I never coded
in golang, before!) to make the  output of comitium matches the gemlog
specification.

This way  clients can subscribe to  the feed (if clients  supports the
standard, of course!).

Please consider merging if you find useful.

Bye!
C.

core/entries.go

@@ -142,15 +142,16 @@ func (d *FullData) WriteFeed(dataPath string) error {
 		for _, entry := range pe.Entries {
 			// get just the date it was published
 			pub := toLocalDay(entry.Published)
+			formattedPubDay := entry.Published.Format("2006-01-02")
 			if pub.Before(curDay) {
 				curDay = pub
-				rawPage += fmt.Sprintf("\n\n## %s\n\n", curDay.Format("2006-01-02"))
+				rawPage += fmt.Sprintf("\n\n## %s\n\n", formattedPubDay)
 			}
 
 			if entry.Title == "" {
-				rawPage += fmt.Sprintf("=> %s %s\n", entry.URL, entry.Prefix)
+				rawPage += fmt.Sprintf("=> %s %s %s\n", entry.URL, formattedPubDay, entry.Prefix)
 			} else {
-				rawPage += fmt.Sprintf("=> %s %s — %s\n", entry.URL, entry.Prefix, entry.Title)
+				rawPage += fmt.Sprintf("=> %s %s %s — %s\n", entry.URL, formattedPubDay, entry.Prefix, entry.Title)
 			}
 		}
 	}