title: Vim goes whack with tmux
body: <p><img src="https://i.stack.imgur.com/Jiyvz.png" alt="enter image description here"></p>
  
  <p>NERDTree goes whack in tmux session as in the picture. The same problem exists when windows are split. But now i am using <a href="https://github.com/Lokaltog/powerline" rel="noreferrer">powerline</a> This time the Vim status goes whack(in the picture see the middle portion of the status line) in tmux. What is wrong? </p>