Modify Google-OAuth module to use refresh_token.

Usage

1. To get the refresh_token

	app.all('/auth', function(req, res){

		if( !req.query.code ){
			googleCalendar.getGoogleAuthorizeTokenURL({access_type:'offline'}, function(err, redirectUrl){
				if(err) return res.send(500, err);
				return res.redirect(redirectUrl);
			});
		}else{
			googleCalendar.getGoogleAccessToken(req.query, function(err, accessToken, refreshToken){
				if(err) return res.send(500, err);
				console.log(refreshKey); // store accessToken and refreshToken here
				return res.redirect('/');
			});
		}
	});

2. To use the refresh_token to get new access_token

	googleCalendar.getGoogleAccessToken({code:refreshKey, client_id:google_client_id, client_secret:'jInndhA_LSOGqJ1JO6-WKV-5'}, function(err, accessToken, refreshToken){
		googleAccessKey = accessToken; // store new access key
	});