When Powerline is installed as a package in the system-wide
site-packages folder it can easily be enabled by adding a simple python
statement to the user's vimrc file.
Otherwise it can be added by doing a :source
path/to/plugin/vim/powerline.vim in vimrc, but the other way of doing it
works without specifying the full path as long as Powerline is installed
somewhere in sys.path.