Allow spaces in description

The description included in the otpauth URL needs to be encoded. I guess strictly speaking the secret cannot have characters that need encoding, but I added that anyway.

https://kimmo.suominen.com/stuff/google-authenticator-spaces.diff

I would have uploaded to trac, but google-authenticator was not in the list of available modules for creating a new ticket.

Thanks for a great plugin!

https://www.ads-software.com/extend/plugins/google-authenticator/