Added and corrected comments

generator.go

@@ -13,10 +13,13 @@ type Generator struct {
 	Text    string `xml:"text"`
 }
 
+// NewGenerator creates a new Generator. It returns a *Generator.
 func NewGenerator(text string) *Generator {
 	return &Generator{Text: html.UnescapeString(text)}
 }
 
+// Check checks the Generator for incompatibilities with RFC4287. It returns an
+// error.
 func (g *Generator) Check() error {
 	if g.URI != "" {
 		if !isValidIRI(g.URI) {