This simple json string is parsed incorrectly (testcase)

Program:

```
extern crate json;
fn main() {
    let text = r##"{"no":"w","yes":"q","no":"x"}"##;
    let j = json::parse(text).unwrap();
    println!("{:?}", j["yes"]);
    println!("{:?}", j["no"]);
}
```

Output:
```
Short("x")
Null
```

Expected Output:
```
Short("q")
Short("x")
```