def update
      options = self.class.merge_options()
      options.merge!({:body => self.to_xml})
      response = self.class.put(self.href, options)
      begin 
        self.class.check_status_code(response)
      rescue
        return false
      end
      return true
    end
def update
      options = self.class.merge_options()
      options.merge!({:body => self.to_xml})
      response = self.class.put(self.href, options)
      begin 
        self.class.check_status_code(response)
      rescue
        return false
      end
      return true
    end
Updates the object on server, after attributes have been set.
 Returns boolean if successful

 Example:
   te = Cashboard::TimeEntry.new_from_url(time_entry_url)
   te.minutes = 60
   update_success = te.update