Optimize GoldSrc RCON requests

Only send second request if authentication succeeded.
Fix SteamId missing fetchMembers method

This bug was introduced by refactoring SteamId caching in
bb4bb6be3da7995dceb3dd696430b3112356822d.
Merge branch 'pingers-1.3-stable' into 1.3-stable

Fix SteamId missing fetchMembers method
Use vendored PHPUnit
Add HHVM to tested PHP versions