Minimized show_topology example
Add sample .conf file
Add external attribute to output.
Add features test for topology C API
Refactor and merge apps/topology to trema.
Rename libtopology -> topology.  C API part for #3.
Move .features to match new features/ directory structure.
Add event filter operation.
I compile step definition should build in trema C compatible options.
Auto start topology daemon. (#5)
Kill topology before/after libtopology unittests
Merge branch 'fix_read_pid_check' into topo-trema-C
Suppress invalid option error message.