Fixed all H2 headings

Before, H2 fomratting was not consistent.
Now, all H2 headings use over/under asterisks.

docs/scenarios/json.rst

@@ -9,8 +9,10 @@ The `json <https://docs.python.org/2/library/json.html>`_ library can parse
 JSON from strings or files. The library parses JSON into a Python dictionary
 or list. It can also convert Python dictionaries or lists into JSON strings.
 
+
+************
 Parsing JSON
-------------
+************
 
 Take the following string containing JSON data:
 
@@ -46,8 +48,9 @@ You can also convert the following to JSON:
     '{"first_name": "Guido", "last_name": "Rossum", "titles": ["BDFL", "Developer"]}'
 
 
+**********
 simplejson
-----------
+**********
 
 The JSON library was added to Python in version 2.6.
 If you're using an earlier version of Python, the