How can i rotate the camera with the mouse around the player?

Now it's rotating in space i can rotate the camera around but not around the player. I want the camera to be rotating only around the player.

using UnityEngine;
using System.Collections;

public class CameraMover : MonoBehaviour
{
    public float speedH = 2.0f;
    public float speedV = 2.0f;
    private float yaw = 0.0f;
    private float pitch = 0.0f;

    public Transform playerTransform;
    public Transform mainCameraTransform = null;
    private Vector3 cameraOffset = Vector3.zero;
    public float turnSpeed = 3;

    void Start()
    {
        mainCameraTransform = Camera.main.transform;

        //Get camera-player Transform Offset that will be used to move the camera 
        cameraOffset = mainCameraTransform.position - playerTransform.position;
    }

    void LateUpdate()
    {
        //Move the camera to the position of the playerTransform with the offset that was saved in the begining
        mainCameraTransform.position = playerTransform.position + cameraOffset;

        yaw += speedH * Input.GetAxis("Mouse X");
        pitch -= speedV * Input.GetAxis("Mouse Y");
        mainCameraTransform.eulerAngles = new Vector3(pitch, yaw, 0.0f);
    }
}

I'm using now eulerAngles for the rotation.