Revert "Release version v0.2.5-rc019."

This reverts commit 8082ba1cdd4e5124484f9397553b0f1aa4be427e.
Revert "Add gem install bundler in vm installer."

This reverts commit 1be204465de412aa3782cee438b6c19a1e86b41b.
Release version v0.2.5-rc020.