------------------
- Add new parameter ``lazy_load`` to ``AsdfFile.open``. It is ``True`` by
default and preserves the default behavior. ``False`` detaches the
loaded tree from the underlying file: all blocks are fully read and
numpy arrays are materialized. Thus it becomes safe to close the file
and continue using ``AsdfFile.tree``. However, ``copy_arrays`` parameter
is still effective and the active memory maps may still require the file
to stay open in case ``copy_arrays`` is ``False``. [573]
- Add ``AsdfConversionWarning`` for failures to convert ASDF tree into custom
types. This warning is converted to an error when using
``assert_roundtrip_tree`` for tests. [583]
- Deprecate ``asdf.AsdfFile.open`` in favor of ``asdf.open``. [579]
- Add readonly protection to memory mapped arrays when the underlying file
handle is readonly. [579]