add synchronised has_path? to capybara

capybara.rb

module Capybara
  class Session
    def has_path?(path)
      synchronize do
        current_path == path or raise Capybara::ExpectationNotMet
      end
    end

    def synchronize(seconds=Capybara.default_wait_time)
      start_time = Time.now

      begin
        yield
      rescue => e
        raise e if (Time.now - start_time) >= seconds
        sleep(0.05)
        retry
      end
    end
  end
end