Error when using double colon in selector

The parser fails on the first occurrence of a double colon in https://github.com/necolas/normalize.css/ (using version 1.3.11 of https://github.com/css/csso):

``` css
button::-moz-focus-inner,
input::-moz-focus-inner {
  border: 0;
  padding: 0;
}
```
