RFC: Add Events to Raven

*Please do not accept this pull request yet*

This adds several events:

```javascript
document.addEventListener('ravenHandle', myCallback);
document.removeEventListener('ravenHandle', myCallback);
```

Right now, I'm triggering three events:
- `ravenHandle`: triggers as Raven gets called from TraceKit to handle an error
   - properties added to event object: `stackInfo`, `options`
- `ravenSuccess`: triggers when Raven has successfully reported an error to sentry
   - properties added to event object: `data`, `src`
- `ravenFailure`: triggers when Raven tried to report an error, but got back an bad response code.
   - properties added to event object: `data`, `src`

Discussion Points:
- Callback Names
- Callback Arguments (I definitely do not like what i'm passing now)
- Eventing Mechanism (is it too complex?)

Relevant Issues: #81 and #83

Edit: Updated to match current commits