Destroy does not release the device in the extension

[Michael Guntsche]

node-roon-api-volume-control/lib.js

Line 42 in 87b6885

 delete(this._objs[o.control_key]); 

When destroy is called the local callback is not removed correctly. The key used here should be

delete(this._objs[o.state.control_key]);

Issue #3 is related to this as well.

[Ben Coburn]

I believe this to be fixed in commit 73ce294

[Michael Guntsche]

I can confirm that this change fixes the issue.