update narrative docs about iterable decorator argument
Merge branch 'master' of github.com:Pylons/pyramid
- Fix a memory leak when the configurator's ``set_request_property`` method was
  used or when the configurator's ``add_request_method`` method was used with
  the ``property=True`` attribute.  See
  https://github.com/Pylons/pyramid/issues/1212 .

Closes #1212