Sync doco to current code state

README.md

@@ -153,7 +153,7 @@ SELECT status, content::json->'form' AS form
                  jsonb_build_object('myvar','myval','foo','bar'));
 ```
 
-To access binary content, you must coerce the content from the default `varchar` representation to a `bytea` representation using the `textsend` function. Using the default `varchar::bytea` cast will not work, as the cast will stop the first time it hits a zero-valued byte (common in binary data).
+To access binary content, you must coerce the content from the default `varchar` representation to a `bytea` representation using the `text_to_bytea` function. Using the default `varchar::bytea` cast will **not work**, as the cast will stop the first time it hits a zero-valued byte (common in binary data).
 
 ```sql
 WITH
@@ -174,6 +174,8 @@ WHERE field ilike 'Content-Type';
 --------------+---------------
  image/png    |          8090
 ```
+Similarly, when using POST to send `bytea` binary content to a service, use the `bytea_to_text` function to prepare the content.
+
 To access only the headers you can do a HEAD-Request. This will not follow redirections.
 
 ```sql