Fix #48 linking CI 2.x upgrade notes. Also including an instruction to extend CI_ classes.
diff --git a/user_guide/installation/upgrade_200.html b/user_guide/installation/upgrade_200.html
index 58ed6e5..fa57dfb 100644
--- a/user_guide/installation/upgrade_200.html
+++ b/user_guide/installation/upgrade_200.html
@@ -102,7 +102,11 @@
</p>
-<h2>Step 5: Update your user guide</h2>
+<h2>Step 5: Update Class extension</h2>
+<p>All core classes are now prefixed with <kbd>CI_</kbd>. Update Models and Controllers to extend CI_Model and CI_Controller, respectively.</p>
+
+
+<h2>Step 6: Update your user guide</h2>
<p>Please replace your local copy of the user guide with the new version, including the image files.</p>
</div>