Remove duplicated 'guard bundler' section.
Add echo request message parser (refs #55).
Add echo reply message parser (refs #55).
Add echo request message generator (refs #55).
Add echo reply message generator (refs #55).
Add OpenFlow Hello message generator and parser (refs #57).
Add UTF-8 magic comments.
Add Pio::Hello#to_binary_s (refs #57).
Add new OpenFlow Hello section to README.md (refs #57).
Fix reek warning (refs #57).
Rename Hello#to_binary_s to #to_binary (refs #57).
Merge pull request #66 from trema/feature/of_hello

Feature/of hello
Version bump.
Update changelog.
Merge branch 'release/0.5.0'
Merge tag '0.5.0' into develop

0.5.0
Add missing 'new features' header line.
Notify Travis results to gitter.im.
Version bump.
Set hello message type (=0).