Drop ruby 2.1 and add 2.4. Upgrade gem version
Drop ruby 2.1 and add 2.4. Upgrade gem version

abak-press/geminabox,geminabox/geminabox,geminabox/geminabox,abak-press/geminabox,abak-press/geminabox,geminabox/geminabox,geminabox/geminabox,abak-press/geminabox