Rtbkit 634 http bidding interface example

Adds python implementation of a bid agent using http api.
Yes, this does work. But I am assuming I have to stringify the HTTP body to send it, because all examples I saw, write the body of a POST request as a string. 
So I suppose I could implement either way, as the final representation would  be a string. 
Honestly I did not try HTTP POST  the raw JSON on javascript, and it might even work, but I did in JS what I did in Python (which required stringify).  I will give it a try when I have access to DEV6 and DEV7 again.