Merge dev for v2.2.1

Merge dev for v2.2.0

Merge dev for v2.1.1

Merge dev for v2.1.0

# Conflicts:
#	.gitignore

chore: update CONTRIBUTING.md

feat: EfficientFrontier uses fast vectorized methods of Rebalance (wi…

…thout abs and rel bands)

docs: update docstrings

chore: change version to 1.4.4

test: update tests for PortfolioDCF

chore: update code style by black