asyncio_slow: Add example of wait() from docs.

asyncio_slow/test_parallel.py

@@ -0,0 +1,21 @@
+#https://docs.python.org/3.4/library/asyncio-task.html#example-parallel-execution-of-tasks
+#import asyncio
+import asyncio_slow as asyncio
+
+@asyncio.coroutine
+def factorial(name, number):
+    f = 1
+    for i in range(2, number+1):
+        print("Task %s: Compute factorial(%s)..." % (name, i))
+        yield from asyncio.sleep(1)
+        f *= i
+    print("Task %s: factorial(%s) = %s" % (name, number, f))
+
+tasks = [
+    asyncio.Task(factorial("A", 2)),
+    asyncio.Task(factorial("B", 3)),
+    asyncio.Task(factorial("C", 4))]
+
+loop = asyncio.get_event_loop()
+loop.run_until_complete(asyncio.wait(tasks))
+loop.close()