title: In vim airline, only show git branch, not changes to file
body: <p>I'm using vim with airline. I like that airline shows me the git branch, but I don't want it to show me the lines added/removed/changed. What should I add to my ~/.vimrc file to change that? I know I need to set <code>g:airline_section_b</code> but I'm not quite sure what to set it to.</p>
  
  <p>I tried this, but the syntax is clearly wrong, because it didn't work.</p>
  
  <pre><code>let g:airline_section_b = airline#section#create(['branch'])
  </code></pre>