title: Changing background color in vim at a certain column
body: <p>I'd like to be able to highlight the wrap margin/text width in vim by changing the background color (or maybe just a line?).  A lot of IDEs have this.  I mocked up what I'm talking about:</p>
  
  <p><img src="https://farm4.static.flickr.com/3598/3508086136_6c075936a5_o.jpg" /></p>
  
  <p>Anyone know if this can be done in macvim or gvim?</p>