correct error file name matching on *nix

diff -r 23a39ee21652 rails-test.el
--- a/rails-test.el	Tue Aug 07 09:48:46 2007 -0600
+++ b/rails-test.el	Tue Aug 07 09:55:29 2007 -0600
@@ -42,7 +42,7 @@
   (concat
    append
    (format
-    "\\(#{RAILS_ROOT}\/\\)?\\(\\(\\.\\|[A-Za-z]:\\)?\\([a-z/_.-]+%s\\)\\):\\([0-9]+\\)"
+    "\\(#{RAILS_ROOT}\/\\)?\\(\\(\\.\\|[A-Za-z]:\\)?\\([0-9a-z/_.-]+%s\\)\\):\\([0-9]+\\)"
     (rails-test:file-ext-regexp))
    prepend))