Revert "revert to the deprecated 'Lokaltog/vim-powerline' for stability."

This reverts commit 6034945954ff85bc7f0acd9bc88fd6f41eba59cd.
Revert "removed the deprecated 'Lokaltog/vim-powerline' & added 'Lokaltog/powerline'"

This reverts commit a27d1c25875f44b677fff04b9dc71fd792273a9f.