public static async Task SaveUserAsync(FacebookUser user)
		{
			await new AkavacheEntity ().InsertObjectAsync<FacebookUser> (Const.USER_AKAVACHE_KEY, user);
		}
		public static async Task Login(FacebookUser user)
		{
			var url = ApiUrlHelper.GetLoginUrl();
			await HttpHelper.Post (url, user);
		}
 public static async Task Login(FacebookUser user)
 {
     var url = ApiUrlHelper.GetLoginUrl();
     await HttpHelper.Post(url, user);
 }