Full ISO 8601 datetime by default in VertxLoggerFormatter

Hi, 
how about an ISO8601 as a default datetime format for VertxLoggerFormatter? It may be very helpful for lazy or forgetful users.

Printing 
```
[vert.x-eventloop-thread-0] 2014-01-12T13:21:55.566+01:00 INFO [org.vertx.java.platform.impl.cli.Starter]  Succeeded in deploying verticle
```

instead of current
```
[vert.x-eventloop-thread-1] 13:24:31,090 INFO [org.vertx.java.platform.impl.cli.Starter]  Succeeded in deploying verticle
```

Regards