Update instructions to include Google Maven repository

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=165291982

README.md

@@ -20,18 +20,21 @@ and extend, and can be updated through Play Store application updates.
 
 ## Using ExoPlayer ##
 
-ExoPlayer modules can be obtained via jCenter. It's also possible to clone the
+ExoPlayer modules can be obtained via JCenter. It's also possible to clone the
 repository and depend on the modules locally.
 
-### Via jCenter ###
+### Via JCenter ###
 
 The easiest way to get started using ExoPlayer is to add it as a gradle
-dependency. You need to make sure you have the jcenter repository included in
-the `build.gradle` file in the root of your project:
+dependency. You need to make sure you have the JCenter and Google Maven
+repositories included in the `build.gradle` file in the root of your project:
 
 ```gradle
 repositories {
     jcenter()
+    maven {
+        url "https://maven.google.com"
+    }
 }
 ```
 

extensions/gvr/README.md

@@ -11,17 +11,7 @@ of surround sound and ambisonic soundfields.
 
 ## Getting the extension ##
 
-The easiest way to use the extension is to add it as a gradle dependency. You
-need to make sure you have the jcenter repository included in the `build.gradle`
-file in the root of your project:
-
-```gradle
-repositories {
-    jcenter()
-}
-```
-
-Next, include the following in your module's `build.gradle` file:
+The easiest way to use the extension is to add it as a gradle dependency:
 
 ```gradle
 compile 'com.google.android.exoplayer:extension-gvr:rX.X.X'