Inheritance of package-private args with classes in different packages

[pamalyshev]

For example if we have two classes in different packages:

@FragmentWithArgs
public class ClassInPackageA extends android.app.Fragment {
    @Arg
    String argA;
}

and

@FragmentWithArgs
public class ClassInPackageB extends ClassInPackageA {
    @com.hannesdorfmann.fragmentargs.annotation.Arg
    String argB;
}

Then we'll get compilation error:

Error:(36, 13) error: argA is not public in ClassInPackageA; cannot be accessed from outside package

This is because ClassInPackageBBuilder#injectArguments is trying to access argA by itself.
One solution to this could be is to delegate to ClassInPackageABuilder#injectArguments.
I've created test for this in pamalyshev@dde8b1d