title: Polygon perimeter
body: <p>Given a polygon which is constructed like this:</p>
  
  <pre><code>from shapely.geometry import Polygon
  print Polygon([(0,0), (4,0), (2,4)]).area
  </code></pre>
  
  <p>this correctly computes the area of the triangle. However, if i replace the area attribute with 'perimeter' I get the following message: 
  'Polygon' object has no attribute 'perimeter' which seems absurd. Surely, shapely must be able to find the perimeter of a polygon as easily as the area? I've googled this topic for some time (e.g. 'python shapely perimeter' and 'python polygon perimeter') but no relevant results appear.</p>
  
  <p>So please help me find a command inside shapely that allows me to compute the perimeter of my polygon. </p>