Deprecate support for calling native python callbacks.

README.md

@@ -9,21 +9,22 @@ as frontends to scripts.
 ScriptForm takes a JSON file which contains form definitions. It then
 constructs web forms from this JSON and serves these to users. The user can
 select a form and fill it out. When the user submits the form, it is validated
-and the associated script or Python callback is called. Data entered in the
-form is passed to the script through the environment.
+and the associated script is called. Data entered in the form is passed to the
+script through the environment.
 
 ### Features
 
 - Very rapidly construct forms with backends.
 - Completely standalone HTTP server; only requires Python.
-- Callbacks to any kind of script / program or to Python functions.
+- Callbacks to any kind of script / program that supports environment
+  variables.
 - User authentication support through Basic HTAuth.
 - Validates form values before calling scripts.
 - Uploaded files are automatically saved to temporary files, which are passed
   on to the callback.
 - Multiple forms in a single JSON definition file.
-- Handles script / exception errors, HTML output or lets scripts and Python
-  callbacks stream their own HTTP response to the browser.
+- Handles script / exception errors, HTML output or lets scripts callbacks
+  stream their own HTTP response to the browser.
 
 ### Use-cases