More doco

readme.md

@@ -388,7 +388,10 @@ eg: the non-strict parser will allow this:
 ## IJsonReader and IJsonWriter
 
 These interfaces only need to be used when writing custom formatters and parsers.  They are the low
-level interfaces used to read and write the Json stream.
+level interfaces used to read and write the Json stream and are passed to the callbacks for custom
+parsers and formatters.
+
+### IJsonReader
 
 The IJsonReader interface reads from the Json input stream.  
 
@@ -418,6 +421,8 @@ routine must read each value from the IJsonReader before returning.
 
 *Parse* - parses a typed value from the input stream.
 
+### IJsonWriter
+
 The IJsonWriter interface writes to the Json output stream:
 
     public interface IJsonWriter