Remove callbacks from subscriptions. Closes #46.
Marked some tests as @wip. Changed tox.ini according.
Plugins should be initialized with the hub. Closes #47. Detected bad behavior #49.
Plugin tasks initialization. Closes #48.
Subscriptions should be wrapped into a function. Closes #50.
All tests fixed. Removed wip mark. Closes #45.
Merge branch 'plugin_tasks' into develop