refactor(server): follow recommended project layout, put server in bin

- Put server in bin folder
- See [this
post](http://stackoverflow.com/questions/22380293/recommended-dart-proje
ct-layout-for-public-private-app-server-and-or-test-fil/22380294#2238029
4) for details.

Author: chalin

Chapter_06/server_simple_get_and_put.dart renamed to Chapter_06/bin/server_simple_get_and_put.dart

@@ -1,7 +1,7 @@
 import 'dart:io';
 import 'package:http_server/http_server.dart' show VirtualDirectory;
 
-final String PATH_TO_WEB_CONTENT = "web";
+final String PATH_TO_WEB_CONTENT = "../web";
 
 void main() {
   HttpServer.bind(InternetAddress.LOOPBACK_IP_V4, 3031).then((HttpServer server) {