README.txt: Added warning to Chameleon support introduction

Author: xiaq

CHANGES.txt

@@ -7,12 +7,19 @@ Entries without name were done by Richard Jones.
 
 Features:
 
-- We now have two configurable templating engines, the old Zope TAL
+- Experimental support for the new Chameleon templating engine.
+  We now have two configurable templating engines, the old Zope TAL
   templates (called zopetal in the config) and the new Chameleon (called
   chameleon in the config). A new config-option "template_engine" under
   [main] can take these config-options, the default is zopetal.
   Thanks to Cheer Xiao for the idea of making this configurable *and*
   for the actual implementation! (Ralf)
+  WARNING: Chameleon support is highly experimental and *not* recommended for
+  production use. It has known performance issues and i18n is not yet
+  functioning. It's still under active development. Only use this feature if
+  you want to experiment with Chameleon and/or help with Roundup
+  developement. If you found a bug in Chameleon support, please report after
+  testing against latest Roundup source from the Mercurial repository.
 - issue2550678: Allow pagesize=-1 which returns all results.
   Suggested and implemented by John Kristensen. 
   Tested by Satchidanand Haridas. (Bernhard)