[mod] remove render_pos and rely on render_key
[mod] rendering a constant is nonsensical
[mod] add helper functions to handle constants
[mod] constants have now a key
[mod] update dumper to new RenderWalker API
[mod] simplify drastically path
[mod] handle empty paths
[mod] add helper functions to Position
[mod] add helper to make a position from a tuple
[mod] add defensive raise
[doc] add documentation for PathWalker
[mod] test bounding_box with empty path
[doc] document Position class
[mod] add tests for Position
[doc] add a changelog bullet
[fix] bounding_path of empty list node

The fix is to allow walking on empty list nodes
[doc] move baron rendering in advanced section
[doc] simplify doc on path
[doc] add bounding box doc
[doc] rely on docstring for RenderWalker doc