* I need to add XML namespace support to xe, and make sure the
  .import_xml() method works correctly with namespaces.

* I need to make sure that xe deals correctly with string values that
  might cause broken XML: for example, a string with a single "<" needs
  to be properly escaped.  I also need to make sure that CDATA sections
  are handled sensibly.

* I want to add full ISO 8601 date support, although that is a truly
  frightening prospect.  There is such a staggering range of legal date
  formats in ISO 8601!

* I may change a bunch of the class names in xe to make them more
  consistent with each other and thus easier to learn.
