def kelp_within(kind, selector=nil)
      begin
        within(kind, selector) { yield }
      rescue Capybara::ElementNotFound
        raise Kelp::InvalidScope,
          "Scope '#{selector || kind}' not found on page"
      end
    end
def kelp_within(kind, selector=nil)
      begin
        within(kind, selector) { yield }
      rescue Capybara::ElementNotFound
        raise Kelp::InvalidScope,
          "Scope '#{selector || kind}' not found on page"
      end
    end
Wrapper for Capybara's `within`, but raises Kelp::InvalidScope
 instead of Capybara::ElementNotFound