Added simple denyhosts class.

This class is responsible for recording blacklisted hosts.  The
intention is that each failure will be recorded, and when a threshold
is exceeded that will correspond to a lockout.

Currently the threshold is five failures, leading to a window of
five minutes outage.

i.e. fail five times in a row you cannot login for five minutes.

During the five minute window each new failure pushes that block
back to five minutes.
Wire up the denyhosts class.

Each failure is recorded, and after five failures a five minute lockout
is triggered.

If additional requests are received within that five minute window it
is restarted.