Prefer item content over description

Several feeds have the full item in content but an abbreviated version
in the description. This change will prefer the full item content over
the shorter description if there is any content.

mail.go

@@ -79,7 +79,7 @@ func createEmail(feedName string, feedTitle string, item *gofeed.Item, date time
 	email.setUserAgent(conf)
 	email.FeedURL = account.URI
 	email.ItemURI = item.Link
-	if item.Description == "" {
+	if item.Content != "" {
 		email.Body = item.Content
 	} else {
 		email.Body = item.Description