An alternate to fail2ban that allows clients until they hit the
thresholds, then blocks them. Think of it like a throttle where you can
block for more than one period.
based on gist from @ktheory https://gist.github.com/ktheory/5723534
Modified slightly to use fail2ban `filter` terminology to simplify
Rack::Attack initializer configuration (only one block is requred for
this approach instead of 2)
