updated summary

SUMMARY.md

@@ -1,15 +1,9 @@
 # Summary
 
 * [Quick Start](doc/quick-start.md)
-
-## Concepts
-
-* [Data Format and Document Model](doc/concepts/data-and-document.md)
-* [Attributes](doc/concepts/attributes.md)
-* [Second page's title](page2/README.md)
-    * [Some child page](page2/page2-1.md)
-    * [Some other child page](part2/page2-2.md)
-
-## A second page group
-
-* [Yet another page](another-page.md)
+* Concepts
+  * [Data Format and Document Model](doc/concepts/data-and-document.md)
+  * [Attributes](doc/concepts/attributes.md)
+  * [Heuristic rules](doc/concepts/heuristics.md)
+* [Images](doc/images.md)
+* [FAQ](doc/faq.md)