Add the `Comment` type

comment.go

@@ -0,0 +1,13 @@
+package jiraclient
+
+import (
+	"time"
+)
+
+type Comment struct {
+	Self    string    `json:"self"`
+	Id      string    `json:"id"`
+	Author  User      `json:"author"`
+	Body    string    `json:"body"`
+	Created time.Time `json:created"`
+}