Unitless Css Styles should not be converted to string

#### Expected Behaviour 
```
css -> z-index: 1;
js -> zIndex: 1,
```

#### Actual Behaviour :- 

```
css -> z-index: 1;
js -> zIndex: '1',
```

most of the Css-In-Js libraries do not support string unitless values.

Let me know if i need to send a PR to resolve it.