Fix codingdojo URL (#419)

Author: Daniel Mita

exercises/roman-numerals/metadata.yml

@@ -1,4 +1,4 @@
 ---
 blurb: "Write a function to convert from normal numbers to Roman Numerals."
 source: "The Roman Numeral Kata"
-source_url: "http://codingdojo.org/cgi-bin/wiki.pl?KataRomanNumerals"
+source_url: "http://codingdojo.org/cgi-bin/index.pl?KataRomanNumerals"