Update documentation for Code Formatting plugin and Firestore testing (…

…#393)

README.md

@@ -220,7 +220,9 @@ projects may be published as follows.
 
 Code in this repo is formatted with the google-java-format tool. You can enable
 this formatting in Android Studio by downloading and installing the
-[google-java-format plugin](https://plugins.jetbrains.com/plugin/8527-google-java-format).
+[google-java-format plugin](https://github.com/google/google-java-format).
+The plugin is disabled by default, but the repo contains configuration information
+and links to additional plugins.
 
 To run formatting on your entire project you can run
 ```bash

firebase-firestore/README.md

@@ -13,3 +13,13 @@ Firebase and Google Cloud Platform products, including Cloud Functions.
 All Gradle commands should be run from the source root (which is one level up
 from this folder). See the README.md in the source root for instructions on
 publishing/testing Cloud Firestore.
+
+## Testing
+
+After importing the project into Android Studio and building successfully
+for the first time, Android Studio will delete the run configuration xml files
+in `./idea/runConfigurations`. Undo these changes with the command:
+
+```
+$ git checkout .idea/runConfigurations
+```