method loadPlayerImage doesn't exist

[mastef]

The readme mentions a use-case for loadPlayerImage, however that method doesn't seem to exist

[mastef]

I think it should be getPlayerImage instead

[mastef]

In the same breath, the whole getPlayerImage() and loadConnectedPlayers() logic might work better if a specific callback would be defined when calling it, instead of having one centralised callback that's always called, no matter which request.

Also handling failures on both loading friends and loading pictures would be great. Right now the app doesn't know if the request failed, nor why.

[mastef]

I've added a PR #34 for the loading pictures failure callback