Grouping *_spec.rb (refs #236)

- Refactoring set-eth-src-addr_spec.rb
- Grouping action related tasks into spec:actions
Refactoring set-eth-src-addr_spec.rb (refs #236)
Refactoring send-out-port_spec.rb (refs #236)
Merge branch 'develop' of https://github.com/trema/trema into develop