Merge pull request #921 from chrisbra/doc-wordcount

use wordcount function if available

autoload/airline/extensions/wordcount.vim

@@ -9,11 +9,13 @@ function! s:update()
   if &ft !~ s:filetypes
     unlet! b:airline_wordcount
     return
+  elseif exists("*wordcount")
+    let b:airline_wordcount = printf(s:format, wordcount()['words']).
+          \ g:airline_symbols.space . g:airline_right_alt_sep . g:airline_symbols.space
   elseif mode() =~? 's'
     " Bail on select mode
     return
-  endif
-
+  else
     let old_status = v:statusmsg
     let position = getpos(".")
     exe "silent normal! g\<c-g>"
@@ -29,6 +31,7 @@ function! s:update()
     else
       unlet! b:airline_wordcount
     endif
+  endif
 endfunction
 
 function! airline#extensions#wordcount#apply(...)