public JiraRestClient(string url, string username = null, string password = null, JiraRestClientSettings settings = null)
        {
            url = url.EndsWith("/") ? url : url += "/";

            _clientSettings = settings ?? new JiraRestClientSettings();
            _restClient = new RestClient(url)
            {
                Proxy = _clientSettings.Proxy
            };

            if (!String.IsNullOrEmpty(username) && !String.IsNullOrEmpty(password))
            {
                this._restClient.Authenticator = new HttpBasicAuthenticator(username, password);
            }
        }