Update readme

README.md

@@ -4,7 +4,7 @@
     <br><br>
     <a target="_blank" href="https://www.npmjs.com/package/flexsearch"><img src="https://img.shields.io/npm/v/flexsearch.svg"></a>
     <a target="_blank" href="https://travis-ci.org/nextapps-de/flexsearch"><img src="https://travis-ci.org/nextapps-de/flexsearch.svg?branch=master"></a>
-    <a target="_blank" href="https://coveralls.io/github/nextapps-de/flexsearch?branch=master"><img src="https://coveralls.io/repos/github/nextapps-de/flexsearch/badge.svg?branch=master"></a>
+    <a target="_blank" href="https://coveralls.io/github/nextapps-de/flexsearch?branch=master"><img src="https://coveralls.io/repos/github/nextapps-de/flexsearch/badge.svg?branch=master&v=0"></a>
     <a target="_blank" href="https://www.codacy.com/app/ts-thomas/FlexSearch?utm_source=github.com&amp;utm_medium=referral&amp;utm_content=nextapps-de/flexsearch&amp;utm_campaign=Badge_Grade"><img src="https://api.codacy.com/project/badge/Grade/a896e010f6b4429aa7bc9a89550320a7"/></a>
     <a target="_blank" href="https://github.com/nextapps-de/flexsearch/issues"><img src="https://img.shields.io/github/issues/nextapps-de/flexsearch.svg"></a>
     <a target="_blank" href="https://github.com/nextapps-de/flexsearch/blob/master/LICENSE.md"><img src="https://img.shields.io/npm/l/flexsearch.svg"></a>
@@ -614,8 +614,11 @@ Index methods:
 - <a href="#index.encode">Index.__encode__(string)</a>
 - <a href="#index.export">Index.__export__()</a>
 - <a href="#index.import">Index.__import__(string)</a>
-- <a href="#index.length">Index.__length__()</a>
-- <a href="#index.index">Index.__index__()</a>
+
+Index properties:
+- <a href="#index.id">Index.__id__</a>
+- <a href="#index.length">Index.__length__</a>
+- <a href="#index.index">Index.__index__</a>
 
 ## Usage