Prettify error messages

`From` return was changed, but it's not problem because this method was not released yet.

As discussed in user mailing list.

Allow:
`${errors.from('user.email')}` prints *can't be null, is not a valid e-mail*
`${errors.from('user.email').joint(' - ')}` prints *can't be null - is not a valid e-mail*
`${errors.from('user.email')[0]}` prints *can't be null*