title: Strange behaviour when using radioButton()
body: <p>The code below is giving me some headache.
  It's a very simple application that has 2 radio buttons and a button. The idea of this app is to record in the spreadsheet the value of the radio button selected.
  Now, if I select the 1st radio button("one") and then change to the second radio button("two") and then back to "one" and click the "Record" button, the app will record 3 times in the spreadsheet. It kind of accumulates the selections.</p>
  
  <p>Don't know if I made myself clear, but here are the steps to simulate the issue:</p>
  
  <p>1- Run the application below;
  2- Select radio button "one", then "two" and the "one" again and press the "Record" button;
  3- Check the spreadsheet for duplicated values.</p>
  
  <p>The more you keep clicking the radio buttons, the more duplicated values will be recorded.</p>
  
  <p>Any idea why this happens and how can I overcome this issue?</p>
  
  <pre><code>function myAppFunction() {
  var mydoc = SpreadsheetApp.getActiveSpreadsheet();
  var app = UiApp.createApplication().setTitle('Here is the title bar'); 
  var panel = app.createVerticalPanel().setId('panel');
  
  //using setName will give you the ability to get the value  
  var myRadio1 = app.createRadioButton("group","one").setName('myRadio1').setId('myRadio1');
  var myRadio2 = app.createRadioButton("group","two").setName('myRadio2').setId('myRadio2');
  var button = app.createButton("Gravar").setId("record_");
  //A label will be used to give feedback on the value of the checkBox 
  var infoLabel = app.createLabel('Check the box and click submit').setId('infoLabel');
  
  //handlers 
  var handler = app.createServerChangeHandler('radio1');
  handler.addCallbackElement(panel);  
  myRadio1.addClickHandler(handler);
  
  var handler2 = app.createServerChangeHandler('radio2');
  handler2.addCallbackElement(panel);  
  myRadio2.addClickHandler(handler2);
  
  
  //put everything in the UI 
  panel.add(myRadio1);      
  panel.add(myRadio2); 
  panel.add(button);
  panel.add(infoLabel);
  
  app.add(panel);  
  mydoc.show(app);  
  }
  function radio1(e){
  var app = UiApp.getActiveApplication(); 
  app.getElementById('myRadio2').setValue(false);
  app.getElementById('infoLabel').setText('one is: ' + e.parameter.myRadio1);
  var panel = app.getElementById("panel");
  var button = app.getElementById("gravar");
  var handler = app.createServerClickHandler("record_");
  handler.addCallbackElement(panel);
  button.addClickHandler(handler);
  return app;
  }
  
  function radio2(e){
  var app = UiApp.getActiveApplication(); 
  app.getElementById('myRadio1').setValue(false);
  app.getElementById('infoLabel').setText('two is: ' + e.parameter.myRadio2); 
  var button = app.getElementById("gravar");
  var handler = app.createServerClickHandler("gravar_");
  handler.addCallbackElement(app.getElementById("panel"));
  button.addClickHandler(handler);
  
  return app;
  }
  function record_(e) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheetByName("Sheet1");
  var lastRow = sheet.getLastRow();
  var freeCell = sheet.getRange("A1").offset(lastRow, 0);
  freeCell.setValue(e.parameter.myRadio1);
  }
  </code></pre>