validating an OrderedDict returns an unordered dict

[SimplyKnownAsG]

It would be nice if the returned dictionary from validation were the same type as the original.

For example, if I validate an OrderedDict of (x,y) pairs, the order may be important and converting to a traditional dict doesn't maintain the order. I suppose it is also possible that one could request the validator be ordered as well and I'm not sure what that would mean.

Example:

import numpy
import collections
from voluptuous import Schema, Number

schema = Schema({Number(): Number()}) # x, y pairs (for interpolation or something)
data = collections.OrderedDict(zip(numpy.linspace(5, 100, 11), numpy.random.random(11)))
out = schema(data)
assert isinstance(out, collections.OrderedDict),\
    'Collection is no longer ordered, order:{}'.format(', '.join(str(k) for k in out.keys()))

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This may be related to #40, but I don't quite understand what the issue was there.