Issue #163: Add more cases in the DateTimeParser

Should we use Natty or JChronic when our parser fails?
Merge pull request #166 from ninniuz/163_datetimeparser

Issue #163: Add more cases in the DateTimeParser
Issue #161: Extract years if it is the only info available

- Add the yearParser at the end of the chain of parsers invoked by
PersonDataExtractor
Merge pull request #168 from ninniuz/161_persondata_extract_years_only

Issue #161: Extract years if it is the only info available