Use of url() in CSS can break parsing

Consider the following call:

```js
styleParser('background: url("foo.bpm; display: none; fooled:")')
```

This produces incorrect output:

```js
{
    background: "url(\"foo.bpm",
    display: "none",
    fooled: "\")"
}
```

Whereas it should be `{ background: 'url(...)' }`