Add logToConsole option, and logFunction option

In response to #29. 

```javascript
var notifier = new Notifier();
notifier.configure({ verbose : true }); // will send payloads to window.console.log if defined.
```

```javascript
var fn = function() { ... };
var notifier = new Notifier();
notifier.configure({ logFunction: fn }); // will send payload to fn
```