Add a link with the otpauth url

[jiuka]

To enable Two-factor authentication on a mobile device it would be nice if the otpauth url would not only be encoded as a QR-Code but be provided as a link to. This allows the OTP app to be opened with all the informations as with the QR-Code, but without the haste to take a picture of the mobiles own screen.

https://code.google.com/p/google-authenticator/wiki/KeyUriFormat