Add support for Opera with U2F login

Could you please update u2f_helper.rb to include support for Opera >= version 40 ?

module U2fHelper def inject_u2f_api? ( (browser.chrome? && browser.version.to_i >= 41) || (browser.opera? && browser.version.to_i >= 40) ) && !browser.device.mobile? end end

Thanks, /E