Improve line breaks

[mglukhovsky]

Improve line breaks to follow PEP8 for readability and to improve viewing on narrow screen widths on the website (see http://rethinkdb.com/docs/examples/flask-backbone-todo/).

@chipotle suggests, for example:

Maybe we should treat cases like that as the exception rather than the
rule. We can either add an override class for that code, or -- given that
it's code -- put in actual carriage returns so the lines aren't longer than
78 characters or so to start with. I think the PEP8 style for the snippet
above, for instance, should really be something like:

def patch_todo(todo_id):
    return jsonify(r.table('todos').get(todo_id).update(request.json)
                   .run(g.rdb_conn))

or possibly

def patch_todo(todo_id):
    return jsonify(
        r.table('todos').get(todo_id).update(request.json) .run(g.rdb_conn))

but, the point is we should probably be explicitly setting the line breaks
in code samples.