added quick explanation for the repo's existence

Author: chrislit

README.md

@@ -1,2 +1,6 @@
 # bmpm
 Beider-Morse Phonetic Matching Algorithm
+
+The purpose of this repository is simply to track changes in the reference (PHP) implementation of
+the [Beider-Morse Phonetic Matching Algorithm](http://stevemorse.org/phoneticinfo.htm) to aid
+in my Python port (available as part of [Abydos](https://github.com/chrislit/abydos)).