Bug: Nested navbar items with same title 

I noticed that if you define in the markdown content a structure like:


```
# Title 1
 
foo

## Subtitle

bar

# Title 2
 
foo

## Subtitle

bar


# Title 3
 
foo

## Subtitle

bar
```

The navigation doesn't work correctly when clicking on the nested `subtitles` since the anchor points don't take it's hierarchy position into account. 