Run callbacks when all of loadings occured.

conclude.on('mysql mongo memcache', function(){
	console.log('Ready A')
});
conclude.on(['mysql', 'mongo', 'memcache'], function(){
	console.log('Ready B')
});
conclude.on('mysql', 'mongo', 'memcache', function(){
	console.log('Ready C')
});

var ready = conclude.getReady();
var memcacheReady = conclude.getReady('memcache');

process.nextTick(function(){
	// Notify conclude
	conclude.ready('mysql');
	// Notify with closure
	ready('mongo');
	// Notify with strict closure
	memcacheReady();

}, 3000 * Math.random());