title: How to get all child node values as a array while parent node is selected in jstree checkbox plugin
body: <p>I am working on jstree checkbox plugin and want to get all child node values while parent node is selected.I tried to implement get_checked method but it didn't work.</p>
  
  <p>Below is my code.</p>
  
  <pre><code>&lt;div id="demo"&gt;&lt;/div&gt;
  
  $('#demo').jstree({
  'core' : {
      'data' : [
          { "text" : "adya", "children" : [
              { "text" : "id" },
              { "text" : "name"},
              {"text":"address"}
          ]
          },
          { "text" : "order", "children" : [
              { "text" : "id" },
              { "text" : "order_name" }
          ]}
      ]
  },
  'checkbox':{'two_state':true,'whole_node':false,'tie_selection':false},
  'plugins':['checkbox','themes','ui'] });
  a = [];
  $('#demo').jstree("get_checked",null,true).each(function() 
   { a.push(this.id) });
  console.log(a);
  </code></pre>
  
  <p>Please help me out.</p>