_pprint_dict forces dictionary-style output for objects that inherit from dict

[rcarneva]

Because pprint_thing checks isinstance(thing, dict), it also catches objects that inherit from dict and forces them to print in the {'a':1, ... } format regardless of the object's unicode, str, or repr definitions. On my machine, I've changed the _pprint_dict function to just:

return unicode(seq)

which seems to give the behavior I'm looking for. I see pprint_thing warns against unicode(object) in general due to nested sequences, but since _pprint_dict doesn't do anything with _nest_lvl anyway, I figured it was probably safe.

Allowing proper subclasses of Dict/OrderedDict to format themselves
sounds like a reasonable expectation to me.

I'll have to think this over a bit for corner cases, and the code to do it
looks a little fragile.

pprint_dict should call pprint_thing rather then directly calling repr, and use
nest_lvl when doing it, thanks for the catch.

actually on this one you were right, see closed PR.