smaato exchange connector

I have created a pull request for the Smaato Exchange Connector. I was able to successfully pass the smaato certification at http://dspportal.smaato.com/ 
This is a proposal for the Smaato Exchange Connector.

A few issues to keep in mind:

* Smaato has lots of creative sizes. One will need to configure lots of creatives in bidding_agent_ex.cc. I can make a bidding_agent_ex.cc available for Smaato if needed.

* Smaato sends WINS as GET requests. RTBKIT only allows WINS to be POST requests. This can be easily hacked by changing a few files in RTBKIT or by having NGINX in front of RTBKIT and turning Smaato WIN GET requests into POST requests.
This shouldn't be needed.