public static SerializableSuscription New(string fileName, string name, Uri url, TimeSpan? blockFor)
        {
            var subscription = new SerializableSuscription(fileName) { Name = name, Uri = url };
            subscription.Save();
			subscription.Block(blockFor);
            return subscription;
        }
        public static SerializableSuscription Open(string fileName, TimeSpan? blockFor)
        {
			if (File.Exists(fileName))
			{
	            var json = File.ReadAllText(fileName);
	            if (json.Length > 0)
				{
					var subscription = new SerializableSuscription(fileName);
	                JsonConvert.PopulateObject(json, subscription, SerializerSettings);
					if (subscription.BlockTo < DateTime.Now)
					{
						subscription.Block(blockFor);
						return subscription;
					}
				}
			}
			//Blocked or not exists
            return null;
        }