v0.4.0 is a major refactor in handler types.
:boom: Breaking changes
- `XMLHandler` has been removed: class handlers don't need to inherit from it anymore
- `return_from` now returns the last yielded item instead of the handler
- `HandleMgr` no longer has the confusing `set_handle` method
:rocket: Added
- Several handlers can now be passed to `return_from` / `iter_from`
- More handler variety:
- Regular functions
- `str`/`tuple`/`list` are syntactic sugar for a handler marked with that value, which
simply yields the node
- Classes are instantiated on the fly (if `__init__` has one mandatory parameter, the
node is passed during instantiation); in that case, a `xml_handler` method can be
defined to customize the way yielded items are handled
- It is now possible to use directly `xml_handle_text` in place of `xml_handle_text()`
- Python 3.9 support