Typo fix that drives to a XCode6 compilation error

```
JVFloatLabeledTextField.h:42:2: Prefix attribute must be followed by an interface or protocol
```
![capture decran 2014-06-04 a 12 46 28](https://cloud.githubusercontent.com/assets/54712/3172471/c5e77310-ebd5-11e3-8a31-5539f209c87f.png)