Updating dev environment setup

Author: VesaJuvonen

docs/spfx/set-up-your-development-environment.md

@@ -1,7 +1,7 @@
 ---
 title: Set up your SharePoint Framework development environment
 description: Use Visual Studio or your own custom development environment to build SharePoint Framework solutions. You can use a Mac, PC, or Linux.
-ms.date: 03/09/2018
+ms.date: 08/20/2018
 ms.prod: sharepoint
 ---
 
@@ -32,7 +32,7 @@ Install [NodeJS LTS version](https://nodejs.org).
 - If you are using a Mac, we recommend that you use [homebrew](http://brew.sh/) to install and manage NodeJS. 
 
 > [!NOTE] 
-> Current LTS version of NodeJS is 8.11.3. Notice that 9.x versions are currently not supported with SharePoint Framework development.
+> Current LTS version of NodeJS is 8.11.4. Notice that 9.x or 10.x versions are currently not supported with SharePoint Framework development.
 
 ### Install a code editor
 
@@ -88,6 +88,17 @@ npm install @microsoft/generator-sharepoint --save-dev
 
 For more information about the Yeoman SharePoint generator, see [Scaffold projects by using Yeoman SharePoint generator](toolchain/scaffolding-projects-using-yeoman-sharepoint-generator.md).
 
+
+## Install the developer certificate
+
+The client-side tool chain uses HTTPS endpoint by default, which means that it will also host the 'localhost' with SSL certificate. This simplifies development process with SharePoint Online as it's also hosted using HTTPS endpoint. 
+
+The SharePoint Framework tool chain comes with a developer certificate that you can install for building your custom solutions easily with HTTPS endpoint. To install the developer certificate, enter following command:
+
+  ```
+  gulp trust-dev-cert
+  ```
+
 ## Optional tools
 
 Following are some tools that might come in handy as well: