return the destination stream, fixes issue#23

[ghost]

If this gets merged then I can pipe filed to oppressor to do gzip/deflate compression like this:

var oppressor = require('oppressor');
var filed = require('filed');
var http = require('http');

var server = http.createServer(function (req, res) {
    filed(__dirname + '/data.txt').pipe(oppressor(req)).pipe(res);
});
server.listen(8000);

Issue: #23

[jcrugzz]

@substack the return dest; line in your fork disappeared somehow. Anyway you could fix that until this is merged?