title: Print boost graph with custom vertex label
body: <p>I want to print a Boost Graph having custom(string) vertex labels instead of the default vertex numbering label 0,1,2...</p>
  
  <p>I have initialized the graph as : </p>
  
  <pre><code>typedef adjacency_list &lt;vecS, vecS, directedS, 
                          property&lt;vertex_name_t,string&gt;
                         &gt; Graph;
  
  Graph g;
  set&lt;string&gt; names; 
  map&lt;string,Graph::vertex_descriptor&gt; vertex ;
  
  for(auto it = names.begin() ; it != names.end(); ++it )
         vertex[*it] =  add_vertex(*it,g) ;
  </code></pre>
  
  <p>Now how should I print this graph such that I get edges of the form <code>abc -&gt; xyz;</code> instead of <code>1-&gt;2;</code> </p>