Fix HTML_ATTR rendering (naive)

- was missing spaces between attributes when rendering to org
- was duplicating attributes when rendering to html - now we join / replace
  attributes depending on the name - for now only class & style are appended

org/org.go

@@ -182,14 +182,11 @@ func (w *OrgWriter) writeNodeWithMeta(n NodeWithMeta) {
 	for _, attributes := range n.Meta.HTMLAttributes {
 		w.WriteString("#+ATTR_HTML: ")
 		for i := 0; i < len(attributes)-1; i += 2 {
-			w.WriteString(attributes[i] + " ")
 			if strings.ContainsAny(attributes[i+1], "\t ") {
-				w.WriteString(`"` + attributes[i+1] + `"`)
-			} else {
-				w.WriteString(attributes[i+1])
+				attributes[i+1] = fmt.Sprintf(`"%s"`, attributes[i+1])
 			}
 		}
-		w.WriteString("\n")
+		w.WriteString(strings.Join(attributes, " ") + "\n")
 	}
 	w.writeNodes(n.Node)
 }