Fix ambiguous links

From #24 

```
[WARNING] [APT Parser] Ambiguous link: 'usage.html'. If this is a local link, prepend "./"!
[WARNING] Could not parse date '24 March 2007' from index.apt (expected yyyy-MM-dd format), ignoring!
[WARNING] [APT Parser] Ambiguous link: 'taglist-mojo.html'. If this is a local link, prepend "./"!
```