added build script for .NET 45
added build script for .NET 45

zhangwei900808/SuperWebSocket,jmptrader/SuperWebSocket,jmptrader/SuperWebSocket,v-rawang/SuperWebSocket,zhangwei900808/SuperWebSocket,v-rawang/SuperWebSocket,jogibear9988/SuperWebSocket,v-rawang/SuperWebSocket,kerryjiang/SuperWebSocket,v-rawang/SuperWebSocket,jogibear9988/SuperWebSocket,wangzheng888520/SuperWebSocket,kerryjiang/SuperWebSocket,wangzheng888520/SuperWebSocket