Fix instructions in file README

* Built executable is located in folder ./build/bin/ now.

README.md

@@ -43,6 +43,6 @@ Total Test time (real) =   0.02 sec
 
 ```bash
 $ export GITLAB_USER_NAME="Jane"
-$ cd build && ./helloWorld
+$ ./build/bin/helloWorld
 Hello Jane!
 ```