changed symbol characters to regular ASCII

plugin/umbrella.vim

highlight UmbrellaNone ctermfg=15 ctermbg=1 guifg=White guibg=Red
" Declare signs.
sign define UmbrellaCovered text=°° texthl=UmbrellaCovered
sign define UmbrellaPartial text=÷÷ texthl=UmbrellaPartial
sign define UmbrellaNone text=×× texthl=UmbrellaNone
sign define UmbrellaCovered text=== texthl=UmbrellaCovered
sign define UmbrellaPartial text=-- texthl=UmbrellaPartial
sign define UmbrellaNone text=__ texthl=UmbrellaNone
function! s:Initialize()
    let s:coverage_systems = {