Invalidate serversToPlayersCache on player updates

[md5nake]

This closes #102

[md5nake]

I think this is a better approach than removing caching entirely. The less we query Redis, the better

[ham1255]

thing is even if this cache existed like what i saw in the code, that players frequently change servers which makes cache useless due huge amounts of invalidated stuff

[md5nake]

Even if cache invalidations are frequent, we still invalidate it when an update is made, and in the meantime we might get some cache hits. I think this is the right way to go about it.

[ham1255]

looks good then, i reverted my commit