update link to latest release download zip file

The download button on the page was linked to the oldest version, v0.1. Updated link to point to the latest version, v0.7.

Author: mbren

index.md

@@ -8,6 +8,6 @@ indexed_by_search: false
     <p>The Tableau Server Client is a Python library for the Tableau Server REST API.</p>
     <br />
     <a class="btn btn-primary btn-lg" href="{{ site.baseurl }}/docs" role="button">Get Started</a>&nbsp;&nbsp;
-    <a class="btn btn-primary btn-lg" href="https://github.com/tableau/server-client-python/archive/v0.1.zip" role="button">Download</a>
+    <a class="btn btn-primary btn-lg" href="https://github.com/tableau/server-client-python/archive/v0.7.zip" role="button">Download</a>
 </header>