implementation for : https://hackernoon.com/how-to-make-smart-contracts-upgradable-2612e771d5a2
Proxy : https://ropsten.etherscan.io/address/0xc8ef0a35e32fcbc756a2aad1e2f2f5de7c8cd6ee
v1: https://ropsten.etherscan.io/address/0x0ba3de3e14e907ee0ac8a62c4d9d9edd28bb9fe8
v2: https://ropsten.etherscan.io/address/0xbed51dedbda18be7b91de7ec7a3f95f1ec153e5f
v3: https://ropsten.etherscan.io/address/0xfb2849c1f3099735fbfed67aa99d009a7a71a928