Support ordered Gateways according to capabilities
In order to support the detection of gateways supporting pluggable transports, the geoip service needs to be aware of which gateway supports which transports. For now, the client needs to get a list of gateways for either obfs4 or openvpn, but this can change with the addition of more transports. It would be cool if the geoip service changes could be designed with that in mind. One option could be that the client sends a transport parameter in it's get request and the geoip service only serves a response with the same json structure that already exists including only the matching gateways.