JSR-303 validator failed to initialize

There is an error message in build logs:

```
[ERROR] JSR-303 validator failed to initialize: Unable to create a Configuration, because no Bean Validation provider could be found. Add a provider like Hibernate Validator (RI) to your classpath. (see http://aspects.jcabi.com/jsr-303.html)
```

Let's add Hibernate validator or apache-bval as a dependency to stop complaining.