with a unique identifier.

 * /erp5/object[@id='foo']/title
 * /erp5/object[@gid='2130123']/title

* Add tests

prefix in builded xpath expression.
* Update test according to this modification

this avoid reading entirely the files if they differ during reading.
- Use parser with remove_blank_text flag to normalise output and c14n.
- Do not append tail to xupdate elements if not needed.

- Support xupdate:insert-before element
- Order attributes updates

- Calculate position of node regarding his parent not by counting his position in child_list
- All equals nodes (c14n) are not compared anymore
- Fix last tested bugs

- replace distutill with setuptool 
- append test-cases using docstring
- append buildout setting
- append interface
- eggify