title: Remove line through marker in matplotlib legend
body: <p>I have a <code>matplotlib</code> plot generated with the following code:</p>
  
  <pre><code>import matplotlib.pyplot as pyplot
  
  Fig, ax = pyplot.subplots()
  for i, (mark, color) in enumerate(zip(
      ['s', 'o', 'D', 'v'], ['r', 'g', 'b', 'purple'])):
      ax.plot(i+1, i+1, color=color,
              marker=mark,
              markerfacecolor='None',
              markeredgecolor=color,
              label=i)
  
  ax.set_xlim(0,5)
  ax.set_ylim(0,5)
  ax.legend()
  </code></pre>
  
  <p>with this as the generated figure:
  <img src="https://i.stack.imgur.com/RzznT.png" alt="matplotlib generated figure"></p>
  
  <p>I don't like the lines through the markers in the legend. How can I get rid of them?</p>