- Character encoding is one of the simplest things to get wrong; this module
	should help guide users along the right path. This is much simpler
	in the Unicode-aware Perls. Should this module drop support for
	everything prior to 5.6, or degrade as gracefully as possible?

- Correctness. It's still possible to generate bad XML. Especially in
	safe mode, checks on processing instructions, comments and DOCTYPE
	declarations should be rigorously matched against the spec.

- Control over presentation. How much is too much? Entities vs. CDATA,
	placement of namespace declarations, whitespace. How much control
	should the user be given?
