1. update gem file. Using ruby-2.4.0 as minimum version for bundle up…

…date, as github_changelog_generator cannot be run on ruby-2.7.0(github-changelog-generator/github-changelog-generator#800), and ruby <2.4 will have openssl failures due to brew removed [email protected] recently, this broke my Catalina machine.

2. update changelog

fix change log format

correct 3.3 to 3.3.0.

bump version to 3.2.2

bump version to 3.2.1

release 3.2.0

bump to 3.1.1 for Xcode 9.3

bump to 3.1.1 for Xcode 9.3

bump to 3.1 release (ChartsOrg#3357)

bump to 3.1 release (ChartsOrg#3357)