added "Cors" options in a send request. To use:
  // Create a force server
  WebServer server = new WebServer(... ...  "other parameter" cors:false );

inspired By: https://github.com/chrisbu/dartlang_json_webservice_article_code/blob/master/simpleserver/simpleserver.dart
Merge pull request #11 from kiuz/master

Added CORS to Making Cross-Domain Requests