Option to not render `index.html` by default

[knownasilya]

For example, I want to see what's in a folder, but the folder contains a index.html and at the moment I get that html served to me instead of accessing the folder. So an option to disable that would be handy.

[scothis]

A good solution here may be a flag to specify the welcome file, if you specify blank, then you are effectively disabling the welcome file and will always see the directory listing.