Instead of :

```
'dict' objects are unhashableTraceback (most recent call last):
  File "<builtin>/app_main.py", line 75, in run_toplevel
  File "mk_graph_file.py", line 34, in <module>
    if d['weight'] > 3])
  File "/usr/local/lib/pypy2.7/dist-packages/networkx/classes/graph.py", line 1488, in subgraph
    for n in bunch:
  File "/usr/local/lib/pypy2.7/dist-packages/networkx/classes/graph.py", line 1815, in bunch_iter
    "Node %s in the sequence nbunch is not a valid node."%n)
TypeError: not all arguments converted during string formatting
```

You get:

```
'dict' objects are unhashableTraceback (most recent call last):
  File "<builtin>/app_main.py", line 75, in run_toplevel
  File "mk_graph_file.py", line 34, in <module>
    if d['weight'] > 3])
  File "/usr/local/lib/pypy2.7/dist-packages/networkx/classes/graph.py", line 1488, in subgraph
    for n in bunch:
  File "/usr/local/lib/pypy2.7/dist-packages/networkx/classes/graph.py", line 1815, in bunch_iter
    "Node {} in the sequence nbunch is not a valid node.".format(n))
NetworkXError: Node ('java', 'performance', {'weight': 5}) in the sequence nbunch is not a valid node.
```

    make all doc_strings raw format r''' '''
    correct underline lengths for headings
    fix latex issue in harmonic_centrality
    replace :ticket:, :url:, :doi:, :arxiv:  with links to webpages
    fix spacing with commas before colons so sphinx can parse well
    add "methods" heading in graph class rst files

Mostly doc string tweaks for graph classes, tutorial.
Fixes of blockmodel and antigraph examples
api_changes and release_2.0 updates.

Update adjacency_iter() method to adjacency() and remove adjacency_list()

Make selfloop methods return iterator instead of list in graph class