Tidy up select examples even more.

docs/api.rst

@@ -76,8 +76,7 @@ contexts.
         total = 0
         recvs = [c.call_async(long_running_operation) for c in contexts]
 
-        with mitogen.master.Select(recvs) as select:
-            for recv, (msg, data) in select:
+        for recv, (msg, data) in mitogen.master.Select(recvs):
             print 'Got %s from %s' % (data, recv)
             total += data
 
@@ -108,8 +107,7 @@ contexts.
             ])
         ]
 
-        with mitogen.master.Select(selects) as select:
-            for _, (msg, data) in select:
+        for recv, (msg, data) in mitogen.master.Select(selects):
             print data
 
     .. py:method:: get (timeout=None)

docs/index.rst

@@ -269,8 +269,7 @@ available.
                     for name in dirnames + filenames), 0)
 
     total = 0
-    for recv, msg in Select(c.call_async(usage, '/tmp') for c in contexts):
-        value = result.unpickle()
+    for recv, (msg, value) in Select(c.call_async(usage, '/tmp') for c in contexts):
         print 'Context %s /tmp usage: %d' % (recv.context, value)
         total += value