Update for latest Godot and godot-nim

src/mainpanel.nim

@@ -14,5 +14,5 @@ gdobj MainPanel of Panel:
       if ev.buttonIndex == BUTTON_LEFT:
         getTree().setInputAsHandled()
         let scene = load("res://scene.tscn") as PackedScene
-        getTree().getRoot().addChild(scene.instance())
+        getTree().root.addChild(scene.instance())
         queueFree()

src/stub.nimble

@@ -3,4 +3,4 @@ author        = "Xored Software, Inc."
 description   = "Godot-Nim Project Stub"
 license       = "MIT"
 
-requires "godot >= 0.7.1 & < 0.8.0"
+requires "godot >= 0.7.3 & < 0.8.0"