add note about stage-0 preset. Fix #13.

Author: chenkie

01-Login/README.md

@@ -14,6 +14,8 @@ cd 01-Login
 npm install
 ```
 
+> **Note:** If you are not using create-react-app but are using Babel, you need to add the `stage-0` preset.
+
 ## Set the Client ID and Domain
 
 If you download the sample from the quickstart page, it will come pre-populated with the **client ID** and **domain** for your application. If you clone the repo directly from Github, rename the `auth0-variables.js.example` file to `auth0-variables.js` and provide the **client ID** and **domain** there. This file is located in `src/Auth/`.

02-User-Profile/README.md

@@ -14,6 +14,8 @@ cd 02-User-Profile
 npm install
 ```
 
+> **Note:** If you are not using create-react-app but are using Babel, you need to add the `stage-0` preset.
+
 ## Set the Client ID and Domain
 
 If you download the sample from the quickstart page, it will come pre-populated with the **client ID** and **domain** for your application. If you clone the repo directly from Github, rename the `auth0-variables.js.example` file to `auth0-variables.js` and provide the **client ID** and **domain** there. This file is located in `src/Auth/`.

03-Calling-an-API/README.md

@@ -14,6 +14,8 @@ cd 03-Calling-an-API
 npm install
 ```
 
+> **Note:** If you are not using create-react-app but are using Babel, you need to add the `stage-0` preset.
+
 ## Set the Client ID and Domain
 
 If you download the sample from the quickstart page, it will come pre-populated with the **client ID** and **domain** for your application. If you clone the repo directly from Github, rename the `auth0-variables.js.example` file to `auth0-variables.js` and provide the **client ID** and **domain** there. This file is located in `src/Auth/`.

04-Authorization/README.md

@@ -14,6 +14,8 @@ cd 04-Authorization
 npm install
 ```
 
+> **Note:** If you are not using create-react-app but are using Babel, you need to add the `stage-0` preset.
+
 ## Set the Client ID and Domain
 
 If you download the sample from the quickstart page, it will come pre-populated with the **client ID** and **domain** for your application. If you clone the repo directly from Github, rename the `auth0-variables.js.example` file to `auth0-variables.js` and provide the **client ID** and **domain** there. This file is located in `src/Auth/`.