BUG: Call this->qvtkDisconnectAll() from qMRMLIGTLIOModel() destructor to address #2431 as suggested by Lchauvin.
Merge pull request #19 from tokjun/2431-no-such-slot-error-in-qMRMLIGTLIOModel

BUG: Call this->qvtkDisconnectAll() from qMRMLIGTLIOModel()