Beefed up the README a little.

README.md

@@ -1,2 +1,19 @@
-# stylist
-Style checking for Fortran, PSyclone DSL, etc
+# Stylist
+
+The immediate need was for a code style checking tool which understood Fortran.
+Such things being quite thin on the ground. However very few large software
+projects are implemented in a single language. Thus a tool was developed which
+provided a framework to aid in delivering support for multiple languages and
+multiple style choices.
+
+The project is still in its infancy so only a few rules have been implemented
+and only for fortran.
+
+The framework supports multiple styles, each consisting of multiple rules.
+Each of these may be one of two types, those which treat the source as a text
+file and those which treat it as a parse tree.
+
+In the past we have used text based tools and there's a surprising amount you
+can do with regular expressions. However once context becomes important they
+can become a liability. In those cases it is much better to have the parse
+tree.