Rtbkit 634 http bidding interface example

Adds python implementation of a bid agent using http api.
Yep, that is what happens... if end is used the bidder sends back just one packet, so the exchange between both sides is reduced to 2 packets (req + resp). if wirte is used one extra ACK comes from the router and the bidder sends one extra empty packet on end(). Which makes the entire exchange to use 5 packets. So the time for the entire exchange on the bidder side between the first and last packet goes from ~1ms to ~40ms.