fix docker link

[ci skip]

Author: randy3k

README.md

@@ -241,7 +241,7 @@ It is recommended to add the following in your `.sublime-project` file so that <
 
 ### Docker container
 
-Check https://github.com/SublimeText/UnitTesting/docker
+Check https://github.com/SublimeText/UnitTesting/tree/master/docker
 
 
 ### Credits