Enumerate the exercises

05_greatest_common_divisor.lua

@@ -1,6 +1,8 @@
--- The greatest common divisor (GCD) of two numbers X and Y is, as the
+-- The greatest common divisor (GCD) of two numbers is, as the name
--- name suggests, the largest number which evenly divides both X and
+-- suggests, the largest number which evenly divides both.  Implement
--- Y.  Implement the function below to calculate this.
+-- the function below to calculate this.  It's recommended that you
+-- use Euclid's algorithm but feel free to use another approach if you
+-- want.
 --
 -- Solution --------------------------------------------------------------------
 function greatest_common_divisor(x, y)

README.md

@@ -4,10 +4,12 @@ This repo contains some Lua exercises along with automated tests for
 their solutions.  Each file contains a description of the problem and
 an area for your solution as well as the tests.  Feel free to define
 as many functions and constants as you need in the solution area, but
-do not modify the tests.
+do not modify the tests.  It's recommended that you roughly stick to
+the defined order of the exercises, but feel free to deviate if you
+wish.
 
 To run the tests and check your solution for a given exercise, simply
 run `lua <the-file>`.  For example, if you were working on the
-anagrams exercise, you would run `lua anagrams.lua`.  For each
+anagrams exercise, you would run `lua 08_anagrams.lua`.  For each
 exercise, the tests should run in well under a tenth of a second; if
 it takes longer than this you should try to speed up your solution.