Feature request: provide support for DictComp about simpleeval HOT 5 OPEN

>>> names = dict(a=dict(x=1, y=2), b=dict(z=3))
>>> EvalWithCompoundTypes(names=names).eval('{**a, **b}')
Traceback (most recent call last):
  File "/Users/psurry/Downloads/simpleeval.py", line 395, in _eval
    handler = self.nodes[type(node)]
KeyError: <class 'NoneType'>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/psurry/Downloads/simpleeval.py", line 616, in eval
    return super(EvalWithCompoundTypes, self).eval(expr)
  File "/Users/psurry/Downloads/simpleeval.py", line 389, in eval
    return self._eval(ast.parse(expr.strip()).body[0])
  File "/Users/psurry/Downloads/simpleeval.py", line 401, in _eval
    return handler(node)
  File "/Users/psurry/Downloads/simpleeval.py", line 404, in _eval_expr
    return self._eval(node.value)
  File "/Users/psurry/Downloads/simpleeval.py", line 401, in _eval
    return handler(node)
  File "/Users/psurry/Downloads/simpleeval.py", line 619, in _eval_dict
    return {self._eval(k): self._eval(v) for (k, v) in zip(node.keys, node.values)}
  File "/Users/psurry/Downloads/simpleeval.py", line 619, in <dictcomp>
    return {self._eval(k): self._eval(v) for (k, v) in zip(node.keys, node.values)}
  File "/Users/psurry/Downloads/simpleeval.py", line 398, in _eval
    "Sorry, {0} is not available in this " "evaluator".format(type(node).__name__)
simpleeval.FeatureNotAvailable: Sorry, NoneType is not available in this evaluator
>>> 

>>> ast.dump(ast.parse('{**a}'))
"Module(body=[Expr(value=Dict(keys=[None], values=[Name(id='a', ctx=Load())]))])"

>>> ast.dump(ast.parse('{"a": 1, **a}'))
"Module(body=[Expr(value=Dict(keys=[Str(s='a'), None], values=[Num(n=1), Name(id='a', ctx=Load())]))])"
>>>