title: Add edge-weights to plot output in networkx
body: <p>I am doing some graph theory in python using the networkx package. I would like 
  to add the weights of the edges of my graph to the plot output. How can I do this? </p>
  
  <p>For example How would I modify the following code to get the desired output?</p>
  
  <pre><code>import networkx as nx
  import matplotlib.pyplot as plt
  
  G=nx.Graph()
  i=1
  G.add_node(i,pos=(i,i))
  G.add_node(2,pos=(2,2))
  G.add_node(3,pos=(1,0))
  G.add_edge(1,2,weight=0.5)
  G.add_edge(1,3,weight=9.8)
  pos=nx.get_node_attributes(G,'pos')
  nx.draw(G,pos)
  plt.savefig("path.png")
  </code></pre>
  
  <p>I would like 0.5 and 9.8 to appear on the edges to which they refer in the graph. </p>