Update CHANGELOG.md
Update CHANGELOG.md

Add v 2.1.0 to changelog
fourdigits/react-date-picker,aphillipo/react-date-picker,erisnuts/react-date-picker,erisnuts/react-date-picker,fourdigits/react-date-picker,ayarulin/react-date-picker,marr/react-date-picker,marr/react-date-picker,aphillipo/react-date-picker,ayarulin/react-date-picker