updating contract and web3 methods, using env variables (#2)

added: include contract build and styles

updated: changes related to web3>5.0.0 (#1)

Rename Ropsten/Contracts/greeter.sol to Ropsten/contracts/greeter.sol

Update style.css

Rename Ropsten/static/style.css to Ropsten/static/css/style.css

Create greeter.json

Update and rename Gochain/static/style.css to Gochain/static/css/style.css

Update index.html

Update app.py

Update style.css

Update style.css

Update index.html

Update app.py

Update app.py