[ANN] packetgen 1.3.0 released

packetgen 1.3.0 has been released.

* home: <https://github.com/sdaubert/packetgen>
* bugs: <https://github.com/sdaubert/packetgen/issues>
* doc: <http://www.rubydoc.info/gems/packetgen>

PacketGen provides simple ways to generate, send and capture network
packets.

Known protocols are: Ethernet, IP, IPv6, ARP, ICMP, ICMPv6, UDP, TCP,
ESP and DNS.

Changes:

### 1.3.0 / 2017-01-27

* add DNS header support,
* PCapNG file reading improvement: now take care of link type given in
Interface Description Block to parse packet,
* big internal changes:
  * remove StructFu module
  * use new types in Types modules. These new types keep previous API,
  * use a new base class for header classes: Struct is replaced by
Types::Fields which provides a better and simpler way to define headers,
  * clean up Packet.parse.