startProfiling and stopProfiling should agree on the default name

In [v8-profiler.js](https://github.com/c4milo/node-webkit-agent/blob/master/lib/v8-profiler.js) it seems like [startProfiling](https://github.com/c4milo/node-webkit-agent/blob/master/lib/v8-profiler.js#L212) sets the default name to be

```
name = 'org.nodejs.profiles.cpu.user-initiated.' + (cpuCache.length + 1);
```

Meanwhile, [stopProfiling](https://github.com/c4milo/node-webkit-agent/blob/master/lib/v8-profiler.js#L220) sets the default name to be ''.

It seems like those should be consistent. I'm still wrapping my head around how everything fits together though, so please correct me if I'm confused.