Changelog:
==========
Refactor XPath function call (context=None only as keyword argument)
Add external function support (issue #60)
Some fixes to string representation and source property of tokens
Extend documentation and tests
Clean XSD datatypes hierarchy
Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
