simple JavaScript function that checks if kennitala check digit is correct
ninth digit of Icelandic Social Security Number (kennitala) is a check digit that's how it's calculated: if kennitala is
ABCDEF-GHIJ
I = 11 - ((3xA + 2xB + 7xC + 6xD + 5xE + 4xF + 3xG + 2xH) mod 11)