Added better docs for 'phone2numeric' template filter

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2306 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/templates.txt

@@ -924,7 +924,12 @@ digits. For a string, it's a list of characters.
 phone2numeric
 ~~~~~~~~~~~~~
 
-Converts a phone number to its numerical equivalent.
+Converts a phone number (possibly containing letters) to its numerical
+equivalent. For example, ``'800-COLLECT'`` will be converted to
+``'800-2655328'``.
+
+The input doesn't have to be a valid phone number. This will happily convert
+any string.
 
 pluralize
 ~~~~~~~~~