Too lenient with trailing commas in dicts

[slai]

It looks like the JSON conformance issue mentioned in #50 also affects dicts -

In [1]: import json, ujson

In [2]: json_str = '{"hello": "world",}'

In [3]: json.loads(json_str)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-3-e626482e668e> in <module>()
----> 1 json.loads(json_str)

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.pyc in loads(s, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw)
    336             parse_int is None and parse_float is None and
    337             parse_constant is None and object_pairs_hook is None and not kw):
--> 338         return _default_decoder.decode(s)
    339     if cls is None:
    340         cls = JSONDecoder

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.pyc in decode(self, s, _w)
    364 
    365         """
--> 366         obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    367         end = _w(s, end).end()
    368         if end != len(s):

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.pyc in raw_decode(self, s, idx)
    380         """
    381         try:
--> 382             obj, end = self.scan_once(s, idx)
    383         except StopIteration:
    384             raise ValueError("No JSON object could be decoded")

ValueError: Expecting property name: line 1 column 19 (char 18)

In [4]: ujson.loads(json_str)
Out[4]: {u'hello': u'world'}

[timdawborn]

Fixed in #323.