Log Message:
Update to 4.0. From the changelog:

- Requires XML::Elemental 2.0 for SAX-based parsing.
- Switched internal storage of element and attribute names to
    Clarkian notation.
- Too many bug fixes and minor enhancements to list.
- Added atom, itunes, openSerch, feedburner and creativeCommons
    namespaces to default set.
- Moved XPath namespace and prefixes storage from Element to the
    Parser module.
- Added register_ns_prefix, prefix and namespace methods to parser
    for OO access to the internal hashes.
- Introduced use of Class::ErroHandler for more quieter error
    handling.
- We have tests.
- Introduction of Util module. Moved as_xml and encode_xml methods
    from Element to Util.