title: update options of select when other select change
body: <p>I need to update the options of my second select box when my firt select box change,
  but i dont know how to do this.</p>
  
  <p>I want to select all Stores from Client</p>
  
  <p>my .html.erb</p>
  
  <pre><code>    &lt;div class="field"&gt;
          &lt;%= f.label :client_id %&gt;&lt;br&gt;
          &lt;%= f.select :client_id, Client.all.collect {|c| [c.name, c.id]} %&gt;
      &lt;/div&gt;
  
      &lt;div class="field"&gt;
          &lt;%= f.label :store_id %&gt;&lt;br&gt;
          &lt;%= f.select :store_id, Store.where(:client_id =&gt; :client_id).collect {|l| [store.name, store.id]} %&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>I'm thinking of using JQuery to do this. But how do I update the select box? 
  Is there any simple solution to this?</p>