Soundex: Implements the Soundex Algorithm.
Soundex hashes words to a smaller space using a simple model
which approximates the sound of the word as produced by a native
American English speaker. The hash is a four (usually) character
string in which the first character is an uppercase letter and the
remaining characters are digits. Soundex was originally
intended only for encoding proper last names, but occasionally
finds other uses as well. The Soundex algorithm was devised and
patented by Margaret K. Odell and Robert C. Russell in 1918.