Add a filesystem like GridFS from MongoDB

There is a Guzzle middleware for caching via ETag and such. That could be integrated and offered by this client:

Kevinrob/guzzle-cache-middleware#8 (comment)

Optimize the HTTP Socket Client.

How about a QueryBuilder that could enable stuff like this?

        $result = $this->database->query()
            ->design('users')
            ->view('user-by-username')
            ->key($username)
            ->includeDocs(true)
            ->execute();

I already have something to start from :)

Currently you can access the couchdb database with magic methods, because it should work like the mongodb repo.
But I don't like the magic methods because you don't have control about whats going on and it makes debugging more harder.

So i think this methods should be removed.

Create a logging client for better debugging.

I added some more helpers to the Result class, like this:

    public function getFirstDoc()
    {
        $row = $this->getFirstRow();

        return $row ? $row['doc'] : false;
    }

    public function getDocs()
    {
        return array_map(function($row) {
            return $row['doc'];
        }, $this->getRows());
    }

    public function isEmpty()
    {
        return !(bool)$this->data['rows'];
    }

    public function isError()
    {
        return array_key_exists('error', $this->data);
    }

    public function isNotFound()
    {
        return $this->isError() && ($this->data['error'] == 'not_found');
    }

Maybe these could be usefull in your Result class.

Guzzle does offer using Promise structures for their responses.
How about using these to offer parallel requests to CouchDB?

How about changing the Namespace from CouchDB\ to something, that will most likely not collide with other software?