add link to lab tutorial

initial-reverse/README.md

@@ -1,7 +1,7 @@
 
 # Introduction
 
-**Before beginning:** Read this [lab tutorial](lab-tutorial.pdf); 
+**Before beginning:** Read this [lab tutorial](http://pages.cs.wisc.edu/~remzi/OSTEP/lab-tutorial.pdf);  
 it has some useful tips for programming in the C environment.
 
 This project is a simple warm-up to get you used to how this whole

initial-utilities/README.md

@@ -1,6 +1,9 @@
 
 # Unix Utilities
 
+**Before beginning:** Read this [lab tutorial](http://pages.cs.wisc.edu/~remzi/OSTEP/lab-tutorial.pdf);  
+it has some useful tips for programming in the C environment.
+
 In this project, you'll build a few different UNIX utilities, simple versions
 of commonly used commands like **cat**, **ls**, etc. We'll call each of them a
 slightly different name to avoid confusion; for example, instead of **cat**,