You can't let him get to this composition without taking damage, if he does you're in trouble. I recommend a push with hydra ling when he's trying to take his 3rd or even before depending on the timing, you can do some damage as he should only have 1 collossus or 2 void rays out depending on what build order he went for. Get hydra range first to help with zoning.
From there you can either do a mutalisk switch if the stalker count is low and hope it catches him off guard or you can tech up to vipers and add roaches and more hydra. Either way, keep the pressure up while maintaining a good economy and don't let him get to your base with 200/200 because you can't beat it in a single fight, you'll need to hit, remax and re-engage if he gets his deathball up. Certainly don't let him get a 4th base.
Watch some life replays from IEM New York, he floods lings to kill the 3rd, seems quite effective but then again life is life