Add iptables package

packages/iptables.rb

+require 'package'
+
+class Iptables < Package
+  description 'iptables is the userspace command line program used to configure the Linux 2.4.x and later packet filtering ruleset.'
+  homepage 'https://www.netfilter.org/projects/iptables/'
+  version '1.6.1'
+  source_url 'https://www.netfilter.org/projects/iptables/files/iptables-1.6.1.tar.bz2'
+  source_sha256 '0fc2d7bd5d7be11311726466789d4c65fb4c8e096c9182b56ce97440864f0cf5'
+
+  def self.build
+    system './configure \
+            --disable-nftables'
+    system 'make'
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end