update readme for pyexcel-io plugins

Author: chfw

templates/README.rst.jj2

@@ -116,6 +116,12 @@ Continue from previous example:
 As a pyexcel plugin
 --------------------------------------------------------------------------------
 
+No longer, explicit import is needed since pyexcel version 0.2.2. Instead,
+this library is auto-loaded. So if you want to read data in {{file_type}} format,
+installing it is enough.
+
+Any version under pyexcel 0.2.2, you have to keep doing the following:
+
 Import it in your file to enable this plugin:
 
 .. code-block:: python