Instead of hard coding user_id and comment_author parameter, set them in default array

Instead of hard coding user_id and comment_author parameter, set them in default array and then merge the received parameters with our defaults one, so that user_id received in $attr is not overridden by default arguments.
Merge pull request #490 from UmeshSingla/patch-3

Use default array for attrs
Merge branch 'master' into develop