In pandas.DataFrame.to_dict add an option for dict keys to be strings instead of integers
to_dict is an ideal option for exporting data to json format. Unfortunately, python "json" (json.dumps) package doesn't accept keys as integers, it expects strings only and throws TypeError when it receives anything else. This is trivial to workaround, however in terms of speed, it'd better to have a choice to either have string keys or integers.
