Default HTML document in directory

I've got a simple website and I've got a directory with GM scripts there (but that's not important).
The only thing I can do there is to access it using FTP and make directories and create files and folders.
Now I've got this structure:

/
here are normal website files
gmscripts/
    index.html (?)
    script.js
    script2.js

and I'd like to achieve that if I go to http://ift.tt/2xMoQIR it shows me the index.html file (or any other specific file). How can I do this?

Thank you for answer!

P.S.: I can also use php, but I'd like to avoid this!