Migrated base files from apps/topology
Add show_switch_status command
Add a binary heap implementaion.
Add utility functions for binary heap.
Add heap_utility_test.c
* Moved show_{topology,switch_status} to examples/topology
* Minimized show_topology example
* Add sample .conf file
* Add external attribute to show_switch output.
Refactor and merge apps/topology to trema.
Rename libtopology -> topology.  C API part for #3.
Add event filter operation. (#2)
I compile step definition should build in trema C compatible options.
Auto start topology daemon. (#5)
Fix a issue where read_pid was failing when a trema name was specified with -n or --name option.
Suppress invalid option error message.
Fix build on 32bit environment.
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.
Removed Map API (#8)