update example to be less dependent on internals.

README.md

@@ -13,8 +13,7 @@ Lean & mean statusline for vim that's light as air.
 *  Extensive suite of themes for popular colorschemes including [solarized][23] (dark and light), [tomorrow][24] (all variants), [base16][32] (all variants), [molokai][25], [jellybeans][26] and others; have a look at the [screenshots][14] in the wiki.
 *  Supports 7.2 as the minimum Vim version.
 *  Stable release cycle; bleeding edge changes happen on the `dev` branch, and after they have gone through a [full regression test][33] will eventually be merged in the stable master branch.  Releases typically occur every 2 weeks.
-
-[![Build Status](https://travis-ci.org/bling/vim-airline.png)](https://travis-ci.org/bling/vim-airline)
+*  Unit tests: [![Build Status](https://travis-ci.org/bling/vim-airline.png)](https://travis-ci.org/bling/vim-airline)
 
 ## Straightforward customization
 

autoload/airline/extensions/example.vim

@@ -25,10 +25,14 @@ endfunction
 function! airline#extensions#example#apply(...)
   " First we check for the filetype.
   if &filetype == "nyancat"
-    " Let's use a helper function.  It will take care of ensuring that the
-    " window-local override exists (and create one based on the global
-    " airline_section if not), and prepend to it.
-    call airline#extensions#prepend_to_section('x', airline#parts#get('cats').raw)
+
+    " Let's say we want to append to section_c, first we check if there's
+    " already a window-local override, and if not, create it off of the global
+    " section_c.
+    let w:airline_section_c = get(w:, 'airline_section_c', g:airline_section_c)
+
+    " Then we just append this extenion to it, optionally using separators.
+    let w:airline_section_c .= ' '.g:airline_left_alt_sep.' %{airline#extensions#example#get_cats()}'
   endif
 endfunction