Fixing problem: validation errors ignored on redirects. Closes #476

In conversation on Issue #476, @lucascs asked me to send this PR to start the bug fix.

Here the gist with the problematic controller as he asked me: [Problematic Controller](https://gist.github.com/renanigt/6f88e6fced50bce47ac9)
it's from the time we didn't have `validator.getErrors()` method, so we had to catch the exception to be able to get the errors. VRaptor 3 inheritance ;)