Fix issues in hello_clock.py (#29)

Closes issue #28 by making both coroutines exit after ~10 minutes.

Author: hoh

examples/hello_clock.py

@@ -1,23 +1,24 @@
 import asyncio
 
 
+async def print_every_minute():
+    "Print minutes for ten minutes"
+    for i in range(10):
+        await asyncio.sleep(60)
+        print(i, 'minute')
+
+
 async def print_every_second():
-    """Print seconds"""
-    while True:
+    "Print seconds for ten minutes"
+    for i in range(10 * 60):
         for i in range(60):
             print(i, 's')
             await asyncio.sleep(1)
 
 
-async def print_every_minute():
-    for i in range(1, 10):
-        await asyncio.sleep(60)
-        print(i, 'minute')
-
-
 loop = asyncio.get_event_loop()
 loop.run_until_complete(
-    asyncio.gather(print_every_second(),
-                   print_every_minute())
+    asyncio.gather(print_every_minute(),
+                   print_every_second())
 )
 loop.close()