Support for request bundling

[mikaeldui]

Would improve performance for multiple queries against a platform/region far away.

Suggested implementation:

var req1 = new SummonerRequest("summonerA");
var req2 = new ChampMasteryRequest(hmmmm); // Placeholder value?

var results = await (new LeagueOfLegendsMultiRequestClient(Server.NA)).SendAsync(req1, req2);

---

Could this be solved by WebSocket support, #50 ?

---

For reference, here are the ping times to euw1.api.riotgames.com from location all around the world (https://tools.keycdn.com/ping):