- formatting

(cherry picked from commit a88be57fb7ef96e914d8a7fb90de375ec7f0befd)
- Updated the :ref:`examples_versioned_history` example such that
mapped columns are re-mapped to
match column names as well as grouping of columns; in particular,
this allows columns that are explicitly grouped in a same-column-named
joined inheritance scenario to be mapped in the same way in the
history mappings, avoiding warnings added in the 0.9 series
regarding this pattern and allowing the same view of attribute
keys.

(cherry picked from commit de62497b03274c860ea2554dfbacb3064ce02c19)