Delete non existing room fix

See issue #81:
According to http://www.easyrtc.com/docs/server/pub.appObj.html, the second parameter of the deleteRoom callback function should return 'true' only if the room was deleted. When I delete a non-existing room, this parameter is still 'true'. I don't get an error, either.

I fixed this issue - see:  easyrtc / lib / easyrtc_public_obj.js line 2409 ff
Trying to delete a non-existing room now returns the following error msg:
"Can't delete non-existing room <roomname>"

I tested the code manually.