A working implementation of ruby-u2f in Sinatra

[konklone]

I just wanted to drop a note to point to my working implementation using ruby-u2f, which I have documented extensively:

https://github.com/konklone/konklone.com/pull/144

It may be helpful to you in developing this library. I'd also love to be shown where I may be making mistakes, or not fully understanding the problem.

I did need to make some changes from the example code shown, such as using as_json before to_json, and Base64-decoding the public key before passing it to the authenticate! step. I also added a lot more conditionals and error handling, and this may be a useful reference point for people going beyond Hello World.