set proxy

set proxy to the module
simple example:

        var NA = require("nodealytics");
        NA.initialize('UA-xxxxxxxx-1', 'google-analytics-page', function () {
	        NA.setProxy("http://this-is-my-proxy-server");
                NA.trackEvent('debug', 'debug', 'debug', function (err, resp) {
                        if (!err && resp && resp.statusCode === 200) {
                                console.log('it worked!');
                        } 
                });
        });