automatically generate index.html for directories like /archives/ or /categories/

[jdeibele]

In testing Blogofile on S3, it works great except for one thing: S3 doesn't really have folders; so something like /archives/ or /category/ doesn't work, it gives a 404.

It'd be nice to have an index.html automatically generated for each directory in _sites. Not only would this work on S3 but it would also allow people to have their directories look pages of their site instead of just a listing of files.