Add note about fixing auth errors

#3

README.md

@@ -20,6 +20,8 @@ Module for MagicMirror² that supports ecobee thermostats.
 }
 ```
 
+Ensure that the user running MagicMirror has write access to the module's directory so that the module can save the authentication token. If you are unable to do this for any reason, you can instead create a `tokens.json` file in the module's directory yourself and chown it to the user who is running MagicMirror.
+
 ## Authorizing the module on your ecobee account
 
 To authorize this application to access your Ecobee:
@@ -35,6 +37,8 @@ The module will check for the completed authorization every 30sec.
 
 If a code is not used for a long time (Magic Mirror is off, module is turned off, etc.) a new authorization may be required.
 
+See the [Installation](#installation) section above for notes about how authorization is stored and how to fix it if it doesn't seem to remember the authorization token.
+
 ## Config Options
 
 | **Option** | **Default** | **Description** |