updated summary

SUMMARY.md

 # Summary
 
 * [Quick Start](doc/quick-start.md)
-* [Concepts][doc/concepts/readme.md]
+* [Concepts](doc/concepts/readme.md)
   * [Data Format and Document Model](doc/concepts/data-and-document.md)
   * [Attributes](doc/concepts/attributes.md)
   * [Heuristic rules](doc/concepts/heuristics.md)