ATLAS-3572:Atlas website: Remove introduction heading

docs/docz-lib/config/menu.js

 export default [
-    "Introduction",
+    "Overview",
     {
         name: "Documentation",
         menu: [

docs/src/documents/Introduction.md → docs/src/documents/Overview.md

 ---
-name: Introduction
+name: Overview
 route: /
-menu: Introduction 
+menu: Overview
 ---
 
-# Introduction
-
-Atlas is Data Governance and Metadata framework for Hadoop
-
-## Overview
+# Overview
 
 Atlas is a scalable and extensible set of core foundational governance services – enabling
 enterprises to effectively and efficiently meet their compliance requirements within Hadoop and