Don't hard set Android play services version fullstackreact#134

Author: Ehesp

android/build.gradle

@@ -20,7 +20,7 @@ android {
 
 dependencies {
     compile 'com.facebook.react:react-native:0.20.+'
-    compile 'com.google.android.gms:play-services-base:9.8.0'
+    compile 'com.google.android.gms:play-services-base:+'
 
     compile 'com.google.firebase:firebase-core:9.8.0'
     compile 'com.google.firebase:firebase-auth:9.8.0'