Directory Indexes

I need directory indexes so I made this tiny hack. Do with it what you will.

How it works:

`404.html` = `404.html`
`about.ejs` = `about/index.html` (preferred way of doing things)
`folder/index.ejs` = `folder/index.html` (how it is right now in `0.14.0`, and it still works)
`index.ejs` = `index.html`

And that's it.

There are no tests. Should I create some?