Creé un nuevo proyecto en Android Studio y agregué una actividad de Google Maps.

Recibo estas advertencias:

warning: com/google/android/gms/maps/GoogleMap.class(com/google/android/gms/maps:GoogleMap.class): major version 51 is newer than 50, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.
warning: com/google/android/gms/maps/SupportMapFragment.class(com/google/android/gms/maps:SupportMapFragment.class): major version 51 is newer than 50, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.
warning: com/google/android/gms/maps/model/LatLng.class(com/google/android/gms/maps/model:LatLng.class): major version 51 is newer than 50, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.
warning: com/google/android/gms/maps/model/MarkerOptions.class(com/google/android/gms/maps/model:MarkerOptions.class): major version 51 is newer than 50, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.
warning: com/google/android/gms/maps/model/Marker.class(com/google/android/gms/maps/model:Marker.class): major version 51 is newer than 50, the highest major version supported by this compiler.
It is recommended that the compiler be upgraded.

Mi conjetura es que tengo un miss-match JDK o algo así. Instalé JDK 7, y cuando hago javac -version veo 1.7.0_65. Cambié en las preferencias de Android Studio la versión del código de bytes del proyecto, pero eso no cambió estas advertencias.

Mi build.gradle tiene esto

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    // You must install or update the Google Repository through the SDK manager to use this dependency.
    compile 'com.google.android.gms:play-services:5.0.77'
    compile 'com.android.support:support-v13:18.0.+'
}

¿Qué debo hacer para corregir estas advertencias, o debería ignorarlas en Android Studio?