Add plugin for NAT (conntrack) metrics
user
```ruby
#!/usr/bin/env ruby
require 'rubygems' if RUBY_VERSION < '1.9.0'
require 'sensu-plugin/metric/cli'
require 'socket'

class Conntrack < Sensu::Plugin::Metric::CLI::Graphite

  option :scheme,
    :description => "Metric naming scheme, text to prepend to .$parent.$child",
    :long => "--scheme SCHEME",
    :default => "#{Socket.gethostname}.conntrack.connections"

  option :table,
    :description => "Table to count",
    :long => "--table TABLE",
    :default => "conntrack"

  def run
    value = `conntrack -C #{config[:table]}`.strip
    timestamp = Time.now.to_i

    output config[:scheme], value, timestamp

    ok
  end

end
```
assistant