title: Use ag in ctrlp + vim
body: <p>I want to use ag (silver searcher) with ctrlp and vim.
  I have this in my .vimrc:</p>
  
  <pre><code>if executable("ag")
      set grepprg=ag\ --nogroup\ --nocolor
      let g:ctrlp_user_command = 'ag %s -l --nocolor -g ""'
  endif
  
  let g:ctrlp_show_hidden = 1
  
  set wildignore+=*/tmp/*,*.so,*.swp,*.zip,*/.tmp/*,*/.sass-cache/*,*/node_modules/*,*.keep,*.DS_Store,*/.git/*
  </code></pre>
  
  <p>I want ctrlp to include hidden files but those are hidden. If I add <code>-u</code> to the ag command it shows all hidden files but doesn't respect the wildignore or .gitignore. Is it possible to make it respect these?</p>