"Hang Closing" option doesn't work.

I can't seem to get closing brackets to outdent automatically using this package.

```python
a = {
1: 2,
3: 4,
}
```

When I type that, and press Enter after the fourth line, the leading whitespace should be removed when I have the "Hang Closing" option checked, but it doesn't.

Atom version: 1:27.2
ide-python version: 1.0.0

在 Atom 中使用 ide-python 1.0.0 并启用 "Hang Closing" 选项重现该示例。跟踪 Enter 如何处理闭合括号的缩进，然后验证所示 Python 字典的前导空白会被移除，同时其他缩进行为保持不变。

由索引模型根据 Issue 内容生成。