Only show root if there is nothing else to show

popState can get called on page load without an original state event. In
this case we only want to show the root if there is no slug to show.

This was effecting Safari and iOS browsers.
The first block wants `!state` and the others want `state`. It could be changed to:

```javascript
if(!state && pathState.slug == ''){
  this.showRoot();
} else if(state){
  if(state.subsection){
    this.showSubsection(state);
    this.highlightSection('section', state.path);
    this.highlightSection('root', '/browse/' + state.section);
  } else {
    this.showSection(state);
    this.highlightSection('root', state.path);
  }
}
```

But I am not sure that is much clearer.