Same-directory grouping

[stuartpb]

It'd make, say, pulling different branches easy if all the entries under the same directory were clustered together.

[stuartpb]

Honestly, sorting is still a big open issue that needs to be figured out much better than it is now. And I'm pretty sure it's going to look something like manual sorting, meaning this would be irrelevant.

[stuartpb]

And it's definitely going to suck if/when I go ahead with #18: http://guide.couchdb.org/editions/1/en/recipes.html#ordering