add/remove program pid file
refactor code to ruby2.0
Merge pull request #30 from iHiroakiKawai/switch_packet_out_drop

fix segfault when switch received packet-out with drop action
Fix broken .feature of learning-switch.
Merge branch 'master' of https://github.com/trema/trema-edge

Conflicts:
	ruby/trema/trema-switch.rb
fix issue#31 add instructions into multipart flow stats reply
fix issue#32 add ruby echo reply handler