added listener

src/main/java/teetime/framework/StageExceptionListener.java

+package teetime.framework;
+
+public abstract class StageExceptionListener {
+
+	private final Thread thread;
+
+	public StageExceptionListener(final Thread thread) {
+		this.thread = thread;
+	}
+
+	public abstract void onStageException(Stage throwingStage);
+
+}