added licence info for those who want to use it elsewhere

Author: Roger Nesbitt

README.md

@@ -1,3 +1,6 @@
 This is the Hangman ruby game we created at Ruby Girls Wellington.
 
 Make sure you download the words.txt and put it in the same directory before running.
+
+Licensed under the Creative Commons Attribution licence.  Do whatever you'd like with the text and code,
+and please add an attribution to Roger Nesbitt and Rails Girls Wellington.