[Twisted-Python] Suggestion for Deferred docs

[snacktime]

I know this would have helped me, maybe it would others.

In the documentation on Deferred's in the howto section,  the examples
that show a blocking operation and then a non blocking operation do
not show what happened to the blocking code, it just conveniently
disappears.  For someone new to async programming it might help to
give an example that shows the blocking code being called via
deferToThread.  In other words show how you would handle blocking
code.  It doesn't matter if there are 10 ways of doing it, just one
example I think would go a long ways to illustrating the complete
idea.  I know when I was reading about Deferreds for the first time, I
was sitting there thinking 'Ok, I know the example doesn't block now
because they just conveniently yanked out the blocking code!!, but
what DID they do with it?'

Chris