Case-sensitive file names

Git informs me that:

```
Cloning into 'logical-induction'...
[...]
warning: the following paths have collided (e.g. case-sensitive paths
on a case-insensitive filesystem) and only one from the same
colliding group is in the working tree:

  'docs/link/Product.html'
  'docs/link/product.html'
```

I guess those two files are not important anyway.