Add third-party-projects page

Opening this based on discussion in https://github.com/apache/incubator-livy-website/pull/14#issuecomment-358512820.

I wasn't able to test the site properly based on my local setup. Hopefully, these are the correct changes. Please let me know if there are any comments.

Thanks!

Author: Lauren Spiegel <lhspiegel@gmail.com>

Closes #15 from LaurenSpiegel/ft/third-party-projects.
diff --git a/site/_data/navigation.yml b/site/_data/navigation.yml
index 446f114..33a9a21 100644
--- a/site/_data/navigation.yml
+++ b/site/_data/navigation.yml
@@ -33,6 +33,8 @@
     url: /community
   - title: Project Committers
     url: /community-members
+  - title: Third-Party Projects
+    url: /third-party-projects
   - title: Issue Tracker
     url: https://issues.apache.org/jira/browse/LIVY
   - title: Source Code
diff --git a/site/third-party-projects.md b/site/third-party-projects.md
new file mode 100644
index 0000000..96511c8
--- /dev/null
+++ b/site/third-party-projects.md
@@ -0,0 +1,36 @@
+---
+layout: page
+title: Livy - Third-Party Projects
+description: Livy ecosystem projects
+group: nav-right
+---
+<!--
+{% comment %}
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements.  See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to you under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License.  You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+{% endcomment %}
+-->
+
+{% include JB/setup %}
+
+## {{ site.data.project.name }} Third-Party Projects
+
+This page lists external projects that add to Livy's ecosystem.
+Please open a pull request [here]({{ site.data.project.website_repository_mirror }}) if you would like to submit other projects.
+
+### Clients
+
+* [node-livy-client](https://www.npmjs.com/package/node-livy-client) - Livy client written in NodeJS
+