message: Use 'dyn' on trait objects.
  This fixes warnings when building with the currently supported
  compilers.
diff: @@ -96,8 +96,8 @@ impl<'a, G> Dot<'a, G>
  where G: NodeIndexable + IntoNodeReferences + IntoEdgeReferences,
  G: GraphProp,
  G: Data<NodeWeight=NW, EdgeWeight=EW>,
  - NF: FnMut(&NW, &mut FnMut(&Display) -> fmt::Result) -> fmt::Result,
  - EF: FnMut(&EW, &mut FnMut(&Display) -> fmt::Result) -> fmt::Result,
  + NF: FnMut(&NW, &mut dyn FnMut(&dyn Display) -> fmt::Result) -> fmt::Result,
  + EF: FnMut(&EW, &mut dyn FnMut(&dyn Display) -> fmt::Result) -> fmt::Result,
  {
  if !self.config.contains(&Config::GraphContentOnly) {
  try!(writeln!(f, "{} {{", TYPE[g.is_directed() as usize]));
  