Pan a camera around in Unity like any modern Strategy game

MousePan.cs

using UnityEngine;

[RequireComponent(typeof(Camera))]
public class MousePan : MonoBehaviour {

    
    #region Settings
    //Default middle mouse
    public int mouseKey = 2;

    public float sensitivity = 0.1f;
    #endregion

    #region Private Properties
    private Vector3 startDragPos;
    private Camera ourCam;
    #endregion

    // Used for self-initialization
	void Awake () {
        //Just in case you ever go mobile
        Input.simulateMouseWithTouches = true;
	}
    
    // Used for reference assignment
    void Start() {
        ourCam = this.camera;
    }
	
    // Update is called once per frame
    void Update () {
        if ( Input.GetMouseButtonDown( mouseKey ) ) {
            startDragPos = Input.mousePosition;
        }

        if ( Input.GetMouseButton( mouseKey ) ) {
            var destination = ourCam.transform.position + (startDragPos - Input.mousePosition);
            ourCam.transform.position = Vector3.Lerp( ourCam.transform.position, destination, Time.deltaTime * sensitivity );
        }
    }
}