Roman numerals kata

The Roman numerals kata attempts to create a conversion mechanism from integers to a Roman representation (a string):

1, 2 and 3 become I, II and III respectively.
5 and 10 become V and X respectively.
6 become VI, as symbols are additive.
4 becomes IV, as symbols are used subtractively (in this case subtracting 1 from 5) to avoid repeating a symbol more than three times in a row.