chore: change version to 1.4.4

test: update tests for PortfolioDCF

chore: update code style by black

chore: black style

chore: update Travis CI yml to test with Python 3.9-3.11

chore: include Python 3.11 in Travis CI tests

test: add new fixture for Indicator class tests

chore: Python runtime version is set to 3.9

refactor: according flake8

test: update tests for new FX data format