title: Vim youcompleteme ycm doesn't work for the file without an extension such like .gitignore
body: <p>When I input the path or file name in .gitignore, the ycm cannot be triggered. How can I config or enable it?
  eg.
  vim .gitginore
  When I input a path in .gitginore, the popup is not triggered.</p>
  
  <p>Below is the config for ycm:</p>
  
  <pre><code>autocmd InsertLeave * if pumvisible() == 0|pclose|endif "close windows when out of insert mode
  "inoremap &lt;expr&gt; &lt;CR&gt; pumvisible() ? "\&lt;C-y&gt;" : "\&lt;CR&gt;"    "Key enter to select
  let g:ycm_collect_identifiers_from_tags_files=1
  let g:ycm_min_num_of_chars_for_completion=2
  let g:ycm_seed_identifiers_with_syntax=1
  let g:ycm_complete_in_comments = 1 "complete in comment
  let g:ycm_complete_in_strings = 1 "complete in string
  let g:ycm_collect_identifiers_from_comments_and_strings = 1 "search comment and string
  let g:ycm_confirm_extra_conf = 0
  let g:ycm_key_invoke_completion = '&lt;C-x&gt;'
  </code></pre>