Allow setHandlers to set the context for each handler not explicitly set

Allows for:
```javascript
App.vent.setHandlers({
  'get:foo': this.getFoo,
  'get:bar': this.getBar
}, this);
```
Instead of:
```Javascript
App.vent.setHandlers({
  'get:foo': {
    handler: this.getFoo,
    context: this
  },
  'get:bar': {
    handler: this.getBar,
    context: this
  }
});
```