Unity editor script which deletes internal editor cache info related asset bundle. Put this script file under an Editor folder.

CleanCache.cs

using UnityEngine;
using UnityEditor;
using System.Collections;

/// <summary>
/// An editor script which deletes cache info.
///
/// NOTE:
///     Delete all AssetBundle content that has been cached by the current application.
///     This function is not available to WebPlayer applications that use the shared cache.
///
/// See Also:
///     http://docs.unity3d.com/Documentation/ScriptReference/Caching.CleanCache.html
///
/// </summary>
public class CacheTools : ScriptableObject 
{
	
    [MenuItem ("Tools/Cache/Clean")]
    public static void CleanCache ()
    {
	if (Caching.CleanCache ()) 
    	{
	    Debug.LogWarning ("Successfully cleaned all caches.");
	}
        else 
        {
	    Debug.LogWarning ("Cache was in use.");
	}
    }
}