Documentation of 'timed' on the 'async.html' webpage should be improved

[thupp]

The documentation on "async.html" states that "timed_sleep(3)" returns after 3 seconds. In my test this only works if I wait for a result as also demonstrated in "test_async.py" (unittest):

res = timed_sleep(3) # returns immediately
res.value # returns after 3 seconds

A correction of "async.html" would be helpful...