Cheb3

Fixed:
- Compatibility with python 3.8

sahuang

Changes:

- Migrated utils to web3.py v6

Features:

- Add `create` / `create2` address calculator

Changes:

- Allow to create contract instances without signer
- Migrated to use web3.py v6

Features:
- Allow interacting with a contract without ABI

Changes:
- Set `signer` to an optional argument for `Contract.__init__()`

Features:
- Allow using `ContractCaller` to call functions in a contract as an alternative
- Add `Contract.get_storage_at()`

Changes:
- Change the value type of `Account.private_key` to hex string

Features:
- Using `Connection` to connect to the HTTPProvider
- Simplifying the contract deployment and interaction