Revert "Upgrading jekyll to the latest version in 2.4 branch"
Revert "Upgrading jekyll to the latest version in 2.4 branch"

This reverts commit f0b3234102c749bd51fc7121cf3086638714e834.

barancev/barancev.github.io,barancev/barancev.github.io,barancev/barancev.github.io