Update link to repository

Author: rdpeng

README.md

@@ -88,7 +88,8 @@ invertible.
 
 In order to complete this assignment, you must do the following:
 
-1.  Clone the GitHub repository containing the stub R files at [URL]
+1.  Clone the GitHub repository containing the stub R files at
+    [https://github.com/rdpeng/ProgrammingAssignment2](https://github.com/rdpeng/ProgrammingAssignment2)
 2.  Edit the R file contained in the git repository and place your
     solution in that file (please do not rename the file).
 3.  Commit your completed R file into YOUR git repository and push your