Need to update markdown markup at regex lesson

[rgaiacs]

In our regular expression, many of the code samples need to have the markup updated. E.g.:

     m = re.search('cite{(.+)}', 'a \\cite{X} b')
     print m.groups()
     ('X',)

should be

~~~
m = re.search('cite{(.+)}', 'a \\cite{X} b')
print m.groups()
~~~{:class="in"}
~~~
 ('X',)
~~~{:class="out"}