Performance improvements when rendering

- Fast path for JSON, XML and plain text rendering

render/xml.go

@@ -0,0 +1,17 @@
+package render
+
+import (
+	"encoding/xml"
+	"net/http"
+)
+
+type xmlRender struct{}
+
+func (_ xmlRender) Render(w http.ResponseWriter, code int, data ...interface{}) error {
+	return WriteXML(w, code, data[0])
+}
+
+func WriteXML(w http.ResponseWriter, code int, data interface{}) error {
+	WriteHeader(w, code, "application/xml")
+	return xml.NewEncoder(w).Encode(data)
+}