augroup ftomni
    autocmd FileType css setlocal omnifunc=csscomplete#CompleteCSS
    autocmd FileType html,markdown setlocal omnifunc=htmlcomplete#CompleteTags
    autocmd FileType javascript setlocal omnifunc=javascriptcomplete#CompleteJS
    autocmd FileType python setlocal omnifunc=jedi#completions
    autocmd FileType ruby setlocal omnifunc=rubycomplete#Complete
    autocmd FileType xml setlocal omnifunc=xmlcomplete#CompleteTags
augroup end