Bumps version to 4.0.0rc4

Bumps version to 4.0.0rc3

Bumps version to 3.1.23 and updates Changelog

Bumps version to 3.1.22 and updates Changelog

Sets release-date for 3.1.21

Bumps version to 3.1.20

Adding Sukrit Khera to contributor list

Adding Sukrit Khera to contributor list

Set release date for 3.1.18

Sets the release date for 3.1.17

Also bump in README