Dataframe.eval(): Negative number in list passed to 'in'-expression causes crash on python 3.4.0
The following crashes on python 3.4.0. It works fine on Python 2.7.5.

```
>>> import pandas
>>> from io import StringIO
>>> data = "foo,bar\n11,12"
>>> df = pandas.read_csv(StringIO(data))
>>> df.eval('foo in [11, 32]')
0    True
dtype: bool
>>> df.eval('foo in [11, -32]')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/core/frame.py", line 1987, in eval
    return _eval(expr, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/eval.py", line 230, in eval
    truediv=truediv)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 635, in __init__
    self.terms = self.parse()
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 652, in parse
    return self._visitor.visit(self.expr)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 314, in visit
    return visitor(node, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 320, in visit_Module
    return self.visit(expr, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 314, in visit
    return visitor(node, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 323, in visit_Expr
    return self.visit(node.value, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 314, in visit
    return visitor(node, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 560, in visit_Compare
    return self.visit(binop)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 314, in visit
    return visitor(node, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 404, in visit_BinOp
    op, op_class, left, right = self._possibly_transform_eq_ne(node)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 357, in _possibly_transform_eq_ne
    right = self.visit(node.right, side='right')
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 314, in visit
    return visitor(node, **kwargs)
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 430, in visit_List
    name = self.env.add_tmp([self.visit(e).value for e in node.elts])
  File "/home/tobias/Envs/qcache-py3/lib/python3.4/site-packages/pandas/computation/expr.py", line 430, in <listcomp>
    name = self.env.add_tmp([self.visit(e).value for e in node.elts])
AttributeError: 'UnaryOp' object has no attribute 'value'
>>> 
```
