Character Control - Grid like movement

Hello, I am having a problem getting my character to move the way I would like. I recently purchased the book (Game Development with Unity) and have been following along with an example they have on how they set the character up. This was a great start... however, I am wanting my character to move more like a grid system setup as typically seen in top-down old-school RPG or strategy games. I am new to Java script and any help would be greatly appreciated.

What I have so far...

     //Widget_Controller: Handles Widget's movement and player input
 
 //Widget's Movement Variables------------------------------------------------------------------
 //These can be changed in the Inspector
 
 var rollSpeed = 6.0;
 var gravity = 20.0;
 var rotateSpeed = 4.0;
 
 //private, helper variables-----------------------------------------------------------------------
 
 private var moveDirection = Vector3.zero;
 private var grounded : boolean = false;
 private var moveHorz = 0.0;
 private var normalHeight = 2.0;
 
 private var rotateDirection = Vector3.zero;
 
 var isControllable : boolean = true;
 
 //cache controller so we only have to find it once----------------------------------------------
 
 var controller : CharacterController ;
 controller = GetComponent(CharacterController);
 //var widgetStatus : Widget_Status;
 //widgetStatus = GetComponent(Widget_Status);
 
 //Move the controller during the fixed frame updates------------
 
 function FixedUpdate() {
 
     //check to make sure the character is controllable and not dead
     
     if(!isControllable)
         Input.ResetInputAxes();
     
     else{
         if (grounded) {
         
             // Since we're touching something solid, like the ground, allow movement
             //Calculate movement directly from Input Axes
             
             moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
             if ( moveDirection != Vector3.zero ) 
             transform.rotation = Quaternion.LookRotation( moveDirection ); // This line will allow him to rotate the direction he is moving
             moveDirection *= rollSpeed;
         
             }
         }
         
         // Apply gravity to end Jump, enable falling, and make sure he's touching the ground
         moveDirection.y -= gravity * Time.deltaTime; 
         
         // Move and rotate the controller
         var flags = controller.Move(moveDirection * Time.deltaTime);  
         controller.transform.Rotate(rotateDirection * Time.deltaTime, rotateSpeed);
         grounded = ((flags & CollisionFlags.CollidedBelow) != 0 );
 
        } 
        
        
 //---------------------------------------------------------------------------------------------------------------------------
 
 
 function IsMoving(){
 
     return moveDirection.magnitude > 0.5;
 }
 
 function IsGrounded(){
 
     return grounded;
 }
 
 
 ////Make the script easy to find 
 @script AddComponentMenu("Player/Widget'sController")