Adds vertical prop, for scaling based on parent height

[kennethormandy]

Add the vertical prop to scale vertically, rather than horiztonally (the default).

<div style={{ height: '75vh' }}>
 <FitText vertical compressor={1.25}>
   <ul>
     <li>Waterfront</li>
     <li>Vancouver City Centre</li>
     <li>Yaletown–Roundhouse</li>
     <li>Olympic Village</li>
     <li>Broadway–City Hall</li>
     <li>King Edward</li>
     <li>Oakridge–41st Avenue</li>
     <li>Langara–49th Avenue</li>
     <li>Marine Drive</li>
   </ul>
 </FitText>
</div>

It might make more sense to have something like scaleDirection="vertical" as the prop.