* Add MultiPaymentSplitter

with ERC20 support on top of the existing PaymentSplitter

* consistency and linting

* Add MultiPaymentSplitter tests

* fix lint

* add changelog entry

* add MultiPaymentSplitter to documentation

* rework PaymentSplitter to include ERC20 support by default

* remove test file for MultiPaymentSplitter

* fix lint

* completelly split erc20 and token tracking

* address some PR comments

* add notice about rebasing tokens

* fix minor error in tests

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>