How can I make my FPS character slide down a angle.

Hi I'm new to Unity and I am following this tutorial for making my character slide down a slope if it is too steep. My script does not have any errors but it just doesn't seem to be doing anything. I would appreciate if someone could tell me what to fix.

 #pragma strict
 var slideDirection : Vector3;                                   //direction of player slide
 var moveDirection : Vector3 = Vector3.zero;
 var canAngleSlide : boolean = true;
 var speedSlide : float = - 0.0;
 var moveSpeed : float = - 0.0;
 var slideControllableSpeed : float = 5.0;                       //speed at where player still has control
 var slideThreshhold : float = 0.88;                                //amount of angle for when the player slides
 var slideTag : String = "slide";                                   //the tag for when the player will slide
 @script RequireComponent (CharacterController)
 function Start () {
     
     }            
 function Update () {
 
 }
 
 function AngleSlide(){
 if (canAngleSlide)                                                                  //toggle can angle slide
     {
         slideDirection = Vector3.zero;                                                  //               
         var hitInfo : RaycastHit;                                                       //store hit information      
         
         if (Physics.Raycast(transform.position, Vector3.down, hitInfo))                 //cast a ray and find objects position and what it hit
         {
             if(hitInfo.collider.tag != slideTag)                                        //if the collider tag name is tagged with slide then exit out
             {
                 return;                                                                 //return home
                 }
                 if (hitInfo.normal.y < slideThreshhold)                                  //if our normal direction on that slope is lessthen slide threshhold
                 {
                     slideDirection = new Vector3(hitInfo.normal.x, 0, hitInfo.normal.z);//the direction for the player to slide, y is set to 0 to keep play
                 }
             }
             if (slideDirection.magnitude < slideControllableSpeed)                      //checks against slide speed, if less then allow some control
             {
                     moveDirection += slideDirection;                                    //this allows for a bit of jerky movement cleanup
             }
             else 
             {
                 moveDirection = slideDirection;                                         //force the slide to go straght down based on slide direction
             }
             if (slideDirection.magnitude > 0)                                           //if player is sliding
             {
                 moveSpeed = speedSlide;                                                 //move player down at slide speed
             }
         }
     }