Whats the deal with argon2? So I recently read an article about the Argon2 hash function.
Now some Questions: 


I heard that it was developed in 2015 so why is it not implemented yet?

If so where is it implemented? ( I think I saw it in KeePass2 )
How strong is it in comparison aginst bcrypt or sha512 or whirlpool?

Is it really that strong against gpu clusters?
It has been implemented, of course. In addition to the reference implementation, there are some crypto libraries with it like libsodium.
It has not yet seen much use in applications or protocols, because it is relatively new and security people tend to be conservative. (And two years simply is not that long.)

Stronger, at least in theory. The resistance to GPGPU does depend somewhat on parameter choices. E.g. the more memory you use, the harder time GPUs have using all their execution hardware.
The argon2d variant is meant to be even more resistant to GPU compute, at possible expense of side channel resistance in comparison to argon2i.