Use a Renderer interface instead of rendering fragments

paragraph.go

@@ -0,0 +1,24 @@
+package gold
+
+import (
+	"io"
+
+	bf "gopkg.in/russross/blackfriday.v2"
+)
+
+type ParagraphElement struct {
+}
+
+func (e *ParagraphElement) Render(w io.Writer, node *bf.Node, tr *TermRenderer) error {
+	pre := "\n"
+	if node.Prev == nil || (node.Parent != nil && node.Parent.Type == bf.Item) {
+		pre = ""
+	}
+
+	el := &BaseElement{
+		Pre:   pre,
+		Token: string(node.Literal),
+		Style: Paragraph,
+	}
+	return el.Render(w, node, tr)
+}