Loads of warinngs after upgrading to xf 1.5

I get the following warnings after upgrading to 1.5 and google play services v25

1>JAVAC : warning : java\lang\Object.class(java\lang:Object.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\hardware\SensorEventListener.class(android\hardware:SensorEventListener.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : java\lang\String.class(java\lang:String.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : java\lang\Throwable.class(java\lang:Throwable.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\hardware\Sensor.class(android\hardware:Sensor.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\hardware\SensorEvent.class(android\hardware:SensorEvent.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : java\util\ArrayList.class(java\util:ArrayList.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\content\BroadcastReceiver.class(android\content:BroadcastReceiver.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\content\Context.class(android\content:Context.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\content\Intent.class(android\content:Intent.class): major version 51 is newer than 50, the highest major version supported by this compiler.
1>JAVAC : warning : android\widget\ImageView.class(android\widget:ImageView.class): major version 51 is newer than 50, the highest major version supported by this compiler.

my android project is using:

<AndroidUseLatestPlatformSdk>True</AndroidUseLatestPlatformSdk>
<TargetFrameworkVersion>v5.1</TargetFrameworkVersion>