Tags should have 2 more fields

[Ritarira]

When a request is made to get a list of tags or to get a single tag the time stamps should be shown.

Current behaviour Request: GET localhost:3000/tags/5

Response: Status 200

{
    "id": 5,
    "name": "romance"
}

Expected behaviour Request: GET localhost:3000/tags/5

Response: Status 200

{
    "id": 5,
    "name": "romance",
    "created_at": "2017-12-04T07:30:35.820Z",
    "updated_at": "2017-12-07T07:12:09.566Z"
}