* minor performance enhancements to DOM and string output
* better performance tests and documentation of the results
* renamed 'ecoxipy.element_output' to 'ecoxipy.pyxom_output' and moved representation classes to module 'ecoxipy.pyxom'
* text nodes are now created by 'ecoxipy.MarkupBuilder', it is no longer the responsibility of the output implementation to detect Unicode strings to create text nodes from
* minor fixes
* fixed problems with representation, ancestors and descendants of 'ecoxipy.pyxom'