title: Calculate number of business days between two days
body: <p>I need to calculate the number of business days between two dates. How can I pull that off using Ruby (or Rails...if there are Rails-specific helpers).</p>
  
  <p>Likewise, I'd like to be able to add business days to a given date.</p>
  
  <p>So if a date fell on a Thursday and I added 3 business days, it would return the next Tuesday.</p>