Fix the load of index pages for folders;

- Add usage page for Index Pages;
Ignore directory through ignore file
Add suport for hosting image files;

- Images can now be embed with `<img>` of markdown
  `![]()`.
- The fallback (no image) is to serve markdown documents;
- Formats supported (by extension): PNG, JPEG, GIF, SVG;
Merge branch 'patch2'