update from Atlas

attic/control/coro_demo.rst

@@ -0,0 +1,13 @@
+>>> def coroutine():
+...     print('coroutine started')
+...     x = yield
+...     print('coroutine received: {!r}'.format(x))
+...
+>>> coro = coroutine()
+>>> next(coro)
+coroutine started
+>>> coro.send(42)
+coroutine received: 42
+Traceback (most recent call last):
+  ...
+StopIteration