initial attempt.

// @sindresorhus @CWSpear 
I haven't seen it used this way, but that doesn't mean very much, haha. I don't have a lot of experience with Node's `EventEmitter`.

But I don't particularly like it... it feels like what you want to do is

```javascript
wiredep(config).on('error', errorHandler);
```

But I get what you're saying. I don't think I like changing how you initialize it either with `wiredep = require('wiredep')()` either, cuz that'd be a breaking change, ya?