Improved dispose structure.

src/SlatedGameToolkit.Framework/GameEngine.cs

@@ -96,7 +96,7 @@ namespace SlatedGameToolkit.Framework {
                     timePassedFromLastRender = 0;
                 }
             }
-            manager.Dispose();
+            manager.removeAllStates();
             stopped = true;
             SDL.SDL_Quit();
             logger.Information("Game engine has stopped.");

src/SlatedGameToolkit.Framework/StateSystem/Manager.cs

@@ -5,7 +5,7 @@ using SlatedGameToolkit.Framework.StateSystem.States;
 
 namespace SlatedGameToolkit.Framework.StateSystem
 {
-    public sealed class Manager : IDisposable {
+    public sealed class Manager {
         public Thread thread;
         private IState currentState;
         private IState nextState;
@@ -114,17 +114,5 @@ namespace SlatedGameToolkit.Framework.StateSystem
                 removeState(state);
             }
         }
-
-        /// <summary>
-        /// Disposes of this manager.
-        /// </summary>
-        public void Dispose()
-        {
-            removeAllStates();
-        }
-
-        ~Manager() {
-            Dispose();
-        }
     }
 }