DontMove-Child

using UnityEngine;
using System.Collections;

public class CameraController : MonoBehaviour {

	public GameObject target;
	private Quaternion desiredRotation;
	private Vector3 offset;

	void Awake () {
		desiredRotation = transform.rotation;
		offset = transform.position;
	}

	void LateUpdate () {
		transform.rotation = desiredRotation;
		transform.position = target.transform.position + offset;
	}
}