Javascript parser swallows errors thrown in command callback

Looks like error is here : https://github.com/mranney/node_redis/blob/master/lib/parser/javascript.js#L213

This try/catch catches also errors thrown from callbacks, but error isn't thrown/emited to client

in case of pubsub message same message will go on for ever

```javascript
var redis = require('redis'),
	r = redis.createClient(3052, '127.0.0.1'),
	r2 = redis.createClient(3052, '127.0.0.1');

r.on('ready', function() {
	r.subscribe('channel');

	r.on('error', function(e){
		console.log(e);
	});

	r.on('message', function(channel, data) {
		console.log(channel, data);
		throw new Error('test');
	});
});

r2.on('ready', function() {
	var i = 0;
	console.log('r2');
	(function p() {
		r2.publish('channel', ++i);
		setTimeout(p, 1000);
	})()
});

```

output: 
```
channel 2
channel 2
channel 2
...
```

#### Ready to merge checklist
- [ ] test(s) in test.js
- [ ] tests will fail without the PR, but succeed once applied
- [x] docs, if applicable
- [ ] merges cleanly
- [x] coding style (4-space indents, looks similar to other code)