title: how get the last week start date and end date based on date in current week ruby
body: <p>how to get the last week start date and end date based on date in current week ruby (Monday - Sunday)</p>
  
  <p>Example: if date is 04-feb-15, then result should be start_date = Monday(26-jan-1015) end_date =  Sunday(1-feb-15)</p>
  
  <p>if date is 27-feb-15, , then result should be start_date = Monday(16-feb-1015) end_date = (22-feb-15)</p>