[Twisted-Python] spread.sturdy reconnect delay

[Paul Boehm]

currently, when spread.sturdy is unable to (re)connect (e.g. because the
connection was refused/server not running), it retries at full
speed.. without any delay.. 

implementing some kind of rate limiting is trivial, but i'm not sure about
the right approach. the issue is current for me, as i'm using sturdy in
my application and wouldn't want it to flood the network too much.

i've come up with the following approaches:
  *) try n times, then wait i seconds, rinse, repeat
  *) try, sleep i, try, sleep i, ...
  *) try, sleep i++, try, sleep i++, ..

suggestions?