Update installation.md (react-native-maps#696)

* Update installation.md

* Adds note about usage of google api key.

Author: securingsincity

docs/installation.md

@@ -76,7 +76,7 @@ After your `Podfile` is setup properly, run `pod install`.
    ```
 
 1. Specify your Google Maps API Key:
-    > To develop is recommended a ***Browser Key*** without refeer restriction. Go to https://console.developers.google.com/apis/credentials to check your credentials.
+    > For development, it is recommended to use a ***Browser Key*** without referrer restrictions. Go to https://console.developers.google.com/apis/credentials to check your credentials.
 
    Add your **Browser** API key to your manifest file (`android\app\src\main\AndroidManifest.xml`):
 
@@ -88,7 +88,7 @@ After your `Podfile` is setup properly, run `pod install`.
          android:value="{{Your Google maps API Key Here}}"/>
    </application>
    ```
-    > If that doesn't work try using an ***Android Key*** without refeer restriction. Go to https://console.developers.google.com/apis/credentials to check your credentials.
+    > If that doesn't work, try using an ***Android Key*** without referrer restrictions. Go to https://console.developers.google.com/apis/credentials to check your credentials.
 
    Add your **Android** API key to your manifest file:
 
@@ -100,6 +100,8 @@ After your `Podfile` is setup properly, run `pod install`.
            android:value="{{@string/ANDROID_GOOGLE_MAPS_API_KEY}}"/>
    </application>
    ```
+   > Note: As shown above, com.google.android.geo.API_KEY is the recommended metadata name for the API key. A key with this name can be used to authenticate to multiple Google Maps-based APIs on the Android platform, including the Google Maps Android API. For backwards compatibility, the API also supports the name com.google.android.maps.v2.API_KEY. This legacy name allows authentication to the Android Maps API v2 only. An application can specify only one of the API key metadata names. If both are specified, the API throws an exception.
+Source: https://developers.google.com/maps/documentation/android-api/signup
 
 1. Ensure that you have Google Play Services installed:
   * For Genymotion you can follow [these instructions](http://stackoverflow.com/a/20137324/1424349).