adding spoiler warning

Author: L. Grondin

rosalind/README

@@ -5,6 +5,11 @@ http://rosalind.info/
 This is a directory to post solutions to Rosalind problems (Rosalind is a
 Project Euler inspired platform for teaching bioinformatics).  
 
+*** SPOILER WARNING ***
+If you intend to learn bioinformatics with rosalind, you'll have
+to resist the tentation of reading the solutions in this directory.
+*** YOU'VE BEEN WARNED ***
+
 Use the file format <id>-<author>.pl replacing <id> with the (lowercase)
 problem ID and <author> with your name.