New key name same as flattened key

[georgestanley]

This is an Enhancement suggestion that I thought would be useful.
Currently, the new key name is a combination of parent-key + delimiter + child-key.
However, there can be a special case when I would like the new key name told be only the child-key.

E.g.
{'foo': {'bar': 'baz', 'qux': 'corge'} }
should be outputted as
{'bar': 'baz', 'qux': 'corge'} instead of
{'foo:bar': 'baz', 'foo:qux': 'corge'}