Add logToConsole option, and logFunction option

In response to #29. 

```javascript
var notifier = new Notifier();
notifier.configure({ logToConsole : true }); // will send payloads to window.console.log if defined, and not over the network to rollbar
```

```javascript
var fn = function() { ... };
var notifier = new Notifier();
notifier.configure({ logFunction: fn }); // will send payload to fn, and not over the network to rollbar
```

Thank You! :)


Cory Virok, @coryvirok <http://twitter.com/coryvirok>
Co-founder and CTO, Rollbar <http://rollbar.com/>


On Sat, Aug 30, 2014 at 3:11 PM, Carl Furrow <notifications@github.com>
wrote:

> In README.md:
>
> > @@ -110,6 +110,38 @@ var _rollbarConfig = {
> >  // init your rollbar like normal, or insert rollbar.js source snippet here
> >  ```
> >
> > +## Log to console.log, instead of sending payload to rollbar
> > +
> > +```javascript
> > +var _rollbarConfig = {
> > +  accessToken: "POST_CLIENT_ITEM_ACCESS_TOKEN",
> > +  logToConsole: true, // Will send to window.console.log if that function is defined by the browser
>
> Yeah, I like that a lot more. I'll get those changes up in the next day or
> so, and will ping you for a re-review at your leisure. Thanks!
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/rollbar/rollbar.js/pull/42/files#r16931986>.
>