Precision for nested calc is not accurate

```
> reduceCSSCalc('calc((100% / 3) * 3)')
'100%'
> reduceCSSCalc('calc(calc(100% / 3) * 3)')
'99.99999%'
```

We also can go deeper lol:

```
> reduceCSSCalc('calc(calc(100% / 30000000) * 30000000)')
'0%'
```

Note that [it works in Firefox and Chrome](https://jsfiddle.net/3qtd127o/):

![](https://i.imgur.com/J7qSiE1.png)