TO DO

* General code and documentation clean-up.

* Writer: better handling of declared namespace?

* Namespace declarations are stored like attributes. Is this
a problem?

* Should accessors representing elements with defaults
return those default values if nothing has been defined?

* lang and base finder that will check for inheritance?

* Relative links processing utility?

* Accessors to special links such as rel="alternate" and
rel="self"?
