Add local_tunnel() context manager to forward a local port to the remote server (like 'ssh -L')
Using 'except [type], [var]:' instead of 'except [type] as [var]:', which doesn't work in Python 2.5
Fix forwarder to work correctly when service is slow to handle data (both for local and remote tunnels)
ECONNRESET is not a real exception when forwarding tcp connections, so we should ignore it.
Merge branch 'local_tunnel' of github.com:lfasnacht/fabric into local_tunnel
Merge remote-tracking branch 'origin/pr/939'