fix and improve airline toggling functionality.

plugin/airline.vim

@@ -58,10 +58,12 @@ function! s:airline_toggle()
     augroup! airline
 
     if exists("s:stl")
-      let [ &stl, &tal, &stal ] = [ s:stl, s:tal, s:stal ]
+      let &stl = s:stl
     endif
+
+    silent doautocmd User AirlineToggledOff
   else
-    let [ s:stl, s:tal, s:stal ] = [ &stl, &tal, &stal ]
+    let s:stl = &statusline
     augroup airline
       autocmd!
 
@@ -78,6 +80,9 @@ function! s:airline_toggle()
             \ exec 'source '.split(globpath(&rtp, 'autoload/airline/themes/'.g:airline_theme.'.vim', 1), "\n")[0]
             \ | call airline#load_theme()
     augroup END
+
+    silent doautocmd User AirlineToggledOn
+
     if s:airline_initialized
       call <sid>on_window_changed()
     endif