[ANN] packetgen 2.2.0 released

packetgen 2.2.0 has been released.

* home: <https://github.com/sdaubert/packetgen>
* bugs: <https://github.com/sdaubert/packetgen/issues>
* doc: <https://github.com/sdaubert/packetgen/wiki>

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

Known protocols are: Ethernet, Dot11, Dot1x, ARP, IP, IPv6, GRE, ICMP,
ICMPv6, UDP, TCP, SNMP, ESP, DNS, IKE, EAP, BOOTP, DHCP and HTTP.

Changes:

### 2.2.0 / 2017-11-29

* Add support for BOOTP, DHCP and HTTP protocols.
* Add Utils.mitm to mount Man-In-The-Middle attacks on local network
(based on ARP spoofing).
* Header::IP now handles IP packets with options. But options are only
handled as one unique string.
* Types::Fields#read may now demultiplex types, ie may return a derived
type from a factory one.
* Add #to_human to Types::IntString and Types::Int.

* Fixes:
** Fix Types::String#read to take care of length_from option as a Proc
** Header::IP::Addr, Header::IPv6::Addr and Header::Eth::Addr now
inherits from Types::Fields, and no more from Header::Base.
** Fix Types::TLV#initialize: type and length options are now taken in
account.
** Remove a useless and undocumented feature from Packet#parse.
** Fix Utils::ArpSpoofer: may now send packets.
** Fix Itils.arp: use config singleton.