Replace ARPRequest/Reply with Pio::Arp::Request/Reply
Add Trema::Port#dpid.
Merge pull request #329 from trema/feature/port_dpid

Add Trema::Port#dpid.
Version bump.
Merge branch 'release/0.4.5' into develop
Enabled guard-bundler.
Finalize OpenFlow application interface properly.
Replace ICMP* classes with Pio::Icmp::Request/Reply.
Updated simple-router
Merge pull request #330 from shun159/feature/pio_arp_simple_router

Updated simple-router
Merge pull request #328 from trema/feature/pio_arp_simple_router

Replace ARPRequest/Reply with Pio::Arp::Request/Reply
Deleted IPAddr class
Merge pull request #331 from shun159/feature/pio_arp_simple_router

Deleted IPAddr Class
Move all methods in RouterUtils to SimpleRouter.
Pio 0.3.0.
fixed a crash issue when receives a response packet