Add URL and HTMLURL to Issue

Signed-off-by: Ondrej Kupka <ondra.cap@gmail.com>

github/issues.go

@@ -31,6 +31,8 @@ type Issue struct {
 	ClosedAt  *time.Time `json:"closed_at,omitempty"`
 	CreatedAt *time.Time `json:"created_at,omitempty"`
 	UpdatedAt *time.Time `json:"updated_at,omitempty"`
+	URL       *string    `json:"url,omitempty"`
+	HTMLURL   *string    `json:"html_url,omitempty"`
 
 	// TODO(willnorris): milestone
 }