Add Topology Ruby API
Fix for libtopology.h -> topology.h. Closes #3.
Add Ruby version of show_topology example. (#4)
Add Ruby version of show_switch_status. (#4)
Add Topology caching Ruby API example change-history.rb (#4)
Refactor Ruby API (#8)
* Remove _ready events.
* Subscribe only if necessary at #start
* Add block callback form to subscribe/unsubscribe
* Do not inherit Hash.
* Rename Cache to Map.
* Prefix send_ for method which sends request to topology daemon.
* send_ methods now return send result.
* Add/Update YARD document.
* Remove raw property status/external
* Some other refactoring before removing non-primitive API.
* Rewrite Ruby API feature.