title: iOS Auto layout in percentage
body: <p>I wanna create  a   simple  iOS application using autolayout that   displays    three   UIViews.    One on  the top,    one on  the left    and 
  the other   on  the right.  The top view    should  be  50  pixels  high    and fills   the horizontal  space completely.   The left    column  should  fill    40% of  the horizontal  space   and should  fill    100%    of  the 
  vertical    space.  The right   column  should  be  60% of  the horizontal  space   and 100%    of  the vertical space. Finally in  the left    UIView  wanna add   a   single  button.</p>