Fix gem that stopped working after commit in mail gem

Since the `2da7c7985c221272f6451b27ab8b41e84e0a6804` commit in `mikel/mail`, this gem has stopped working raising an `Exception`:

```
Failure/Error: validator.validate(person)
     NoMethodError:
       undefined method `tree' for #<Mail::Address:70199044312560 Address: |james@logi.cl| >
```

So I changed the `:tree` to use `:parse` method, this way I'm still able to get the `local`, `domain` and validate the email.