Back SortedSet onto OrderedDict, rename it, and a few typo fixes

import copy

import warnings

from collections import OrderedDict

from django.utils import six

class MergeDict(object):

class SortedSet(object):

    """

    A set which keeps the ordering of the inserted items.

    Currently backs onto SortedDict.

    Currently backs onto OrderedDict.

    """

    def __init__(self, iterable=None):

        self.dict = SortedDict(((x, None) for x in iterable) if iterable else [])

        self.dict = OrderedDict(((x, None) for x in iterable) if iterable else [])

    def add(self, item):

        self.dict[item] = None