添加设计模式及例子，包括：单例、抽象工厂、适配器、桥接、观察者模式

DesignPattern/SingletonPattern/Singleton.cpp

@@ -0,0 +1,11 @@
+//
+// Created by xiemenghui on 2018/7/20.
+//
+
+#include <iostream>
+#include "Singleton.h"
+
+void Singleton::DoSomething()
+{
+    std::cout << "Singleton do something\n";
+}