title: Get class of selected svg element in d3
body: <p>How do i use instance of <code>&lt;rect&gt;</code> of a <code>svg</code> to get it's class?</p>
  <p>I have to remove lines which have same class as the clicked <code>&lt;rect&gt;</code>.</p>
  <p>I tried using <code>selection.class()</code> which obviously didn't work nor did <code>selection.classed()</code> help.</p>