Add Travis CI badge.
Enable guard.
Merge branch 'develop' of https://github.com/yasuhito/ruby_topology into develop
Added CONTRIBUTING.md.
Enable reek and fix code smells.
Trema 0.4.5.
Pio 0.2.7.
Merge https://github.com/yasuhito/ruby_topology

Conflicts:
	lib/link.rb
	lib/topology.rb
	lib/view/graphviz.rb