Update README.md

Author: XINCGer

CircusGameOnFC/README.md

@@ -3,7 +3,7 @@
 ### 开发环境  
 * Unity5.5.0 + VS2013  
 ### 预览  
-![](./Previews/previews1.png)  
-![](./Previews/previews2.png)  
-![](./Previews/previews3.png)  
-![](./Previews/previews4.png)  
+![](./Previews/preview1.png)  
+![](./Previews/preview2.png)  
+![](./Previews/preview3.png)  
+![](./Previews/preview4.png)