update readme with link to GTM demo app

Author: Daniel Jih

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## Unreleased
 
+* Update README with link to our [Google Tag Manager integration demo app](https://github.com/amplitude/GTM-Web-Demo).
+
 ### 3.0.0 (May 27, 2016)
 
 * Add support for logging events to multiple Amplitude apps. **Note this is a major update, and may break backwards compatability.** See [Readme](https://github.com/amplitude/Amplitude-Javascript#300-update-and-logging-events-to-multiple-amplitude-apps) for details.

README.md

@@ -467,11 +467,5 @@ You can also define the path in your RequireJS configuration like so:
 ```
 
 ### Integrating with Google Tag Manager ###
-**Note: we do not officially support Google Tag Manager, but these instructions have been reported to work for people. Proceed at your own risk**
 
-1. Follow the Javascript SDK [Setup Instructions](https://github.com/amplitude/Amplitude-Javascript#setup), steps 1-3.
-2. Call SDK functions in Google Tag Manager using [Custom HTML tags](https://support.google.com/tagmanager/answer/6107167?hl=en) and adding Javascript in this form as the custom tag:
-
-```html
-<script>amplitude.getInstance().logEvent('TAG');</script>
-```
+Amplitude's JS SDK supports integration with Google Tag Manager. Take a look at our [demo application](https://github.com/amplitude/GTM-Web-Demo) for instructions on how to set it up.