Use ES6 generator as listener handler, add namespace support

[hbpoison]

• Use ES6 generator as event handler, code like this looks better.

    socket.on('todo:get', function *(data) {
        var res = yield todos.get;
        this.emit('todo:get', res);
    });

• Fix the calling sequence to middleware -> event listener, the previous one event listener called first, some middleware like logger could not determine the code execution time.

[hbpoison]

• namespace support added.
• update a namespace usage example to the README.md

[mattstyles]

Sorry for the lack of response, been away for a few days. Will look tonight! Cheers!

[mattstyles]

This is certainly something that is on my todo list, thanks for the contribution.

However, it changes the public API exposed by the library. Although I havent implemented test cases yet (sorry about that, most unhelpful I know) I'm basically using a test repo, any PR would certainly have to run there. The npm start command in that repo uses nvm, if you're not using that (or have a different version of 0.11) then alter bin/start to get it going. It's a pretty straight-forward chat application, nothing incredible but I think it uses most of the API defined in 0.3.0.

One thing that does immediately strike me, any namespace implementation would probably have to be transparent, so that socket.on( ... ) would work seamlessly without knowledge of the underlying architecture. Should be simple enough to just expose the default '/' route for this purpose and maintain the defined API whilst adding namespace support should you need it in whatever app you're using koa-socket in. I certainly wouldnt want namespacing to be mandatory.