title: Sorting a collection by multiple fields
body: <p>I need to sort a collection. 
  For example, I have</p>
  
  <pre><code>Austin 12/3/2012   
  Sam 100 12/3/2012   
  Sam 200 14/3/2012   
  Bubly 300 12/3/2012   
  Bubly 300 15/3/2012  
  ram 100 13/3/2012 
  </code></pre>
  
  <p>Now if the sort order is Name, datetime
  then output should be</p>
  
  <pre><code>Austin 12/3/2012    
  Bubly 12/3/2012   
  Bubly 15/3/2012   
  ram 13/3/2012    
  sam 12/3/2012    
  sam 14/3/2012  
  </code></pre>
  
  <p>If he sort order is Datetime , Name then
  it should be </p>
  
  <pre><code>12/3/2012 austin
  12/3/2012 bubly
  12/3/2012 sam
  13/3/2012 ram
  14/3/2012 sam
  15/3/2012 bubly 
  </code></pre>
  
  <p>Accordingly for other items. How do i do this ? How do I take the order of columns for sorting.</p>