Add disabled tree example and fix original basic example

Author: jakezatecky

examples/dist/index.html

@@ -34,6 +34,9 @@ <h2>Basic Example</h2>
       <h2>Custom Icons Example</h2>
       <div id="custom-icons-example"></div>
 
+      <h2>Disabled Example</h2>
+      <div id="disabled-example"></div>
+
       <h2>No Cascading Example</h2>
       <p>
         By default, the check state of a parent is determined by the check state of its children. Similarly, checking or