title: Vim neocomplcache: disable usage prompt
body: <p>I am using Vim with neocomplcache plugin, its feature of usage prompt while completion confused me so much.</p>
  
  <p>It behaved like this: I typed <code>&lt;C-X&gt;&lt;C-U&gt;</code> when the cursor was at the end of <code>os.path.</code>, then not only completion candidates was listed under the line, but also a horizontal split 
  which contained docstring of the first candidate appeared
  at the top. My question is: how to get rid of this feature so that I only get code completion without the usage prompt?</p>
  
  <p><img src="https://i.stack.imgur.com/GIQvl.png" alt="enter image description here"></p>