nested @page in @media causes errors

```
const inlineCSS = require('inline-css');

var input =
`
@media print {
@page {
.root-element {
size: a3;
}
}
}

inlineCSS(input,{url:' '}).then(function(html) {
console.log(html);
}).catch(function(error) {
console.error(error);
});
```

Output:
```
Error: Error: Unexpected } (line 8, char 3)
at module.exports (/Users/ryleyb/src/vue/node_modules/inline-css/lib/inline-css.js:69:15)
at /Users/ryleyb/src/vue/node_modules/inline-css/lib/inlineContent.js:25:27
at /Users/ryleyb/src/vue/node_modules/extract-css/index.js:39:16
at /Users/ryleyb/src/vue/node_modules/batch/index.js:161:14
at _combinedTickCallback (internal/process/next_tick.js:131:7)
at process._tickCallback (internal/process/next_tick.js:180:9)
at Function.Module.runMain (module.js:611:11)
at startup (bootstrap_node.js:158:16)
at bootstrap_node.js:578:3
```

I don't need or expect any particular result of trying to inline this CSS. Just not an error. On my actual page, ignoring the @page would be fine.