rqt_capabilities won't run

No nice visualisation for me :cry: 

```
$ rosrun rqt_capabilities rqt_capabilities 
PluginManager._load_plugin() could not load plugin "rqt_capabilities/CapabilityGraph":
Traceback (most recent call last):
  File "/opt/ros/hydro/lib/python2.7/dist-packages/qt_gui/plugin_handler.py", line 98, in load
    self._load()
  File "/opt/ros/hydro/lib/python2.7/dist-packages/qt_gui/plugin_handler_direct.py", line 54, in _load
    self._plugin = self._plugin_provider.load(self._instance_id.plugin_id, self._context)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rqt_gui_py/ros_py_plugin_provider.py", line 60, in load
    return super(RosPyPluginProvider, self).load(plugin_id, plugin_context)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 71, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rqt_gui/ros_plugin_provider.py", line 94, in load
    return class_ref(plugin_context)
  File "/opt/kobuki_workspace/catkin_ws/src/rqt_capabilities/src/rqt_capabilities/capability_graph.py", line 100, in __init__
    self.__refresh_view()
  File "/opt/kobuki_workspace/catkin_ws/src/rqt_capabilities/src/rqt_capabilities/capability_graph.py", line 136, in __refresh_view
    self.__update_capabilities_graph()
  File "/opt/kobuki_workspace/catkin_ws/src/rqt_capabilities/src/rqt_capabilities/capability_graph.py", line 139, in __update_capabilities_graph
    self.__update_graph_view(self.__generate_dotcode())
  File "/opt/kobuki_workspace/catkin_ws/src/rqt_capabilities/src/rqt_capabilities/capability_graph.py", line 142, in __generate_dotcode
    return generate_dotcode_from_capability_info(self.__spec_index, self.__running_providers)
  File "/opt/kobuki_workspace/catkin_ws/src/rqt_capabilities/src/rqt_capabilities/dotcode.py", line 59, in generate_dotcode_from_capability_info
    graph = interface_graphs[provider.implements]
KeyError: 'minimal_pkg/SpecificMinimal'
```