Compensate for API's stupid-ass positions in highestRole (#721)

* fix edge cases of highestRole not returning the highest role

* fix line length

* move space

* Fix formatting

src/structures/GuildMember.js

@@ -119,7 +119,9 @@ class GuildMember {
    * @type {Role}
    */
   get highestRole() {
-    return this.roles.reduce((prev, role) => !prev || role.position > prev.position ? role : prev);
+    return this.roles.reduce((prev, role) =>
+      !prev || role.position > prev.position || (role.position === prev.position && role.id < prev.id) ? role : prev
+    );
   }
 
   /**