Fix performance which was causing us to fail on a low RAM virtual machine. The findTestNodeForTest function was always returning nil, which caused reloadItem to reload the entire table. Fixed findTestNodeForTest by fixing the initialization error in GFTestViewModel, so that the _map dictionary is not nil when building the test hierarchy.
Merge pull request #135 from paddlefish/master

Fix performance hit due to reloading entire test table after each test