title: Vim ctrlp only works with a git repo
body: <p>The vim plugin ctrl p only works for me into git repo.</p>
  
  <p>Why does it need a .git file?</p>
  
  <p>Be work i mean it is searching my entire machine when no .git file is found.</p>
  
  <p>my settings</p>
  
  <pre><code>let g:ctrlp_working_path_mode = 'ra'
  let g:ctrlp_match_window = 'top,order:ttb,min:1,max:30,results:30'
  let g:ctrlp_custom_ignore = 'node_modules\|vendor/|DS_Store\|git'
  set wildignore+=*/.git/*,*/.hg/*,*/.svn/*,*/.idea/*,*/.DS_Store,*/vendor
  </code></pre>
  
  <p>Also tried:</p>
  
  <pre><code>let g:ctrlp_working_path_mode = 'r'
  let g:ctrlp_working_path_mode = 'c'
  </code></pre>