Note: by default this segment is disabled. Until #923 it may only be enabled by
copying the whole file and changing "enabled" to "true". After #923 it may be
enabled by having `~/.config/powerline/themes/vim/default.json` with the
following contents:
{
"segment_data": {
"trailing_whitespace": {
"display": true
}
}
}
Fixes#388