* added remove_{publisher,subscriber} to TopicsManager
* added remove_connection to TopicsManager
* added remove_{publishing,subscription}_channel to ClientConnection
* added get_{publisher,subscriber}_topics to ClientConnection
* merged if branches
Refactor according to @tust13 suggestion
Improve test coverage
Merge pull request #5 from ef-ctx/rem-subscriber

* added remove_{publisher,subscriber} to TopicsManager