Mixpanel auth signature generation

gistfile1.js

var params = _.extend({
        api_key: MIXPANEL_KEY,
        expire: Math.ceil(Date.now() / 1000) + 5 * 60
    },
    args.params);

    var toSign = Object.keys(params)
        .sort()
        .map(function(key) { return key + '=' + params[key]; })
        .join('');

    params.sig = crypto.createHash('md5').update(toSign+MIXPANEL_SECRET).digest('hex');

    request.get({url: 'http://mixpanel.com/api/2.0/' + args.path + '/', qs: params, json: true})